Digitized by the Internet Archive 
in 2010 with funding from 
The Library of Congress 



http://www.archive.org/details/practicaltreatis02leuc 



PRACTICAL TREATISE 



CONSTRUCTION, HEATING, AND VENTILATION 



OP 



HOT-HOUSES; 



INCLUDING 



CONSERVATORIES, GREEN-HOUSES, GRAPERIES, 



AND OTHER KINDS OF 



HORTICULTURAL STRUCTURES. 



WITH PRACTICAL DIRECTIONS FOR THEIR MANAGEMENT, IN 
REGARD TO LIGHT, HEAT, AND AIR. 



ILLUSTRATED WjJRH NUMEROUS ENGRAVINGS. 



BY ROBERT B. LEUCHARS, 

GARDEN ARCHITECT. 



BOSTON: 
JOHN P. JEWETT AND COMPANY, 

17 & 19 Cornhill. 
1851. 



V 



Entered according to Act of Congress, in the year 1S50, 
By John P. Jewett & Co., 
In the Clerk's Office of the District Court of the District of Massachusetts. 



Stereotyped by 

HOBART & ROBBINS; 

NEW ENGLAND TYPE AND STEREOTYPE F0UNDERY, 

BOSTON. 



TO 

CJ)is treatise, 

DEBIGJTED TO PBOMOTE THE ABVAXCBMBM1 OP EXOTIC H0ET1CULTUEE. 
OP WHICH HE IS A ZEALOUS PATROL AOT ALMXEEE, 

E7 HI3 OBLIGED A5D 0BEDIE5T SEE7A5T. 

THE AUTHOR. 



PREFACE 



Having for many years past devoted my attention 
to the subjects treated of in this work, and from the 
general call for appliable information thereon, I have 
been induced to give it to the public, in the full 
persuasion that it will be acceptable to horticultur- 
ists, gardeners, and others engaged in this depart- 
ment of horticulture. From the numerous inquiries 
which I have received, there appears to be a great 
want of practical knowledge on these subjects ; and 
though much information may be gleaned from vari- 
ous English works, they are either unobtainable, or 
the information is inapplicable to the wants of this 
country. 

When I commenced this treatise, I intended it as 
a series of articles for periodical publication ; but 
the development of the subjects, and the accumula- 
tion of facts, swelled it to such a size as to render 
its publication in that form impossible. In prepar- 
ing it for the press, in its present form, I have been 
desirous to add nothing but what is necessary to a 
full understanding of the subject in hand, and have 
given figures and diagrams where illustration is 
required. 

The changes which have occurred, during the last- 
twenty years, in the method of constructing and 



TI PREFACE. 



managing horticultural structures, render the works 
of that period of little value to gardeners at the 
present day. I have here given all the latest im- 
provements and most approved methods at present 
in use, with plans and suggestions for their further 
improvement. 

From what has been said, I hope no one will sup- 
pose that this treatise is given as a complete work 
on Exotic Horticulture, Much has yet to be learned, 
on many points connected with hot-houses, which 
futurity will, no doubt, unfold. 

My warmest expressions of thanks are due to 
Professor Dana, of Yale College, for the generous 
manner in which he has favored me with his opinions. 
The readiness with which that gentleman has replied 
to my inquiries, on matters of science relating to 
my subject, even in the midst of his laborious literary 
pursuits, shows how willing he is to aid the most 
humble inquirer. This expression of thanks is due 
from me here, as the only way in which I can suf- 
ficiently show the high value at which I estimate 
his kindness and liberality. 

R. B. L. 

Boston, Oct. 3, 1850. 



INTRODUCTION 



The object of the following treatise is chiefly to lay before 
its readers a series of facts and observations relating to the con- 
struction and general management of all kinds of horticultural 
structures, drawn from the developments of science, and an 
extended experience, with the view of leading those who are 
interested in this delightful pursuit to a more practical inquiry 
regarding the comparative cost and economy of the various 
methods now commonly adopted, as well as to draw the atten- 
tion of practical gardeners to the utility of studying the theory 
as well as the practice of those manifold operations on which the 
success of exotic horticulture depends. 

In a short treatise, on such comprehensive and varied subjects, 
it is impossible to be strictly scientific ; but we have endeavored 
to show the rationale of those methods and operations which we 
have here recommended, and which have been successfully car- 
ried out by us iu practice. The treatise is avowedly a practical 
one, and intended chiefly for the use of practical gardeners, and 
those desirous of obtaining that knowledge which is necessary to 
enable them to superintend the erection and future management 
of their own garden structures. In the management of hot- 
houses, there is a systematic regularity required in all the oper- 
ations, a neglect of which is generally attended with disorder 
and confusion. In fact, there is a system, the details of which 
succeed each other like the links of a chain, each operation being 
essentially connected with the one immediately following and 
preceding it ; and here we have a most encouraging truth, that 
the more scientific our principles of working, the more simple 
and easily performed are our operations, and the more reliable 
are the results. 



8 INTRODUCTION. 

It is doubtful if any branch of horticulture has received less 
aid from science than that which forms the subject of the present 
work. Science has indeed been brought to bear upon horticul- 
tural generalities, but, as far as regards its application to exotic 
horticultural details, it is little better than a sealed book; and 
hence it is that we find cultivators clinging to antiquated sys- 
tems, which the plain demonstrations of science and practice are 
daily proving to be absurd. Amateurs, who adopt exotic horti- 
culture as an amusement, and pursue it with enthusiasm, are 
very apt to be misled by the advice of those who are more igno- 
rant than themselves. They are easily led into extremes ; and 
nothing is more common than for such persons, in their zeal, 
to adopt one error, under the plausible pretext of avoiding 
another. 

From the importance of Light, Heat, and Am, in the econo- 
my of vegetable life, it is obvious why an architect is profession- 
ally incapable of constructing a house for the growth of plants 
or exotic fruits, without possessing a knowledge of the require- 
ments and functions to be performed by the silent inhabitants ; 
and hence it is, that, by studying these principles in connection 
with other branches of science, we arrive at the end more rapidly 
and successfully. In other words, cultivation becomes more cer- 
tain as it becomes more scientific. Practical illustrations will 
hereafter be given, to show that horticultural structures, instead 
of being subordinate to architectural arrangements, as they gen- 
erally are, must be accommodated to the necessities and require- 
ments of vegetable life, before satisfaction can be afforded to the 
possessor, or cultivation carried on in perfection. 

If we take a glance at the progress of horticulture in Europe 
during the last twenty years, we cannot fail to perceive that its 
advancement has been parallel with the developments of chemi- 
cal and physiological science. Almost every succeeding year 
has brought with it some new and important improvement in 
practice, and thrown additional light upon some hitherto disputed 
question. Although gardening has, in some solitary instances, 
been remaining stationary, the cause is by no means obscure. 
Gardening is encouraged just in proportion to the satisfaction 
it affords. It gives satisfaction according to its success, and 



INTRODUCTION. 9 

success is in proportion to the amount of practical experience 
founded upon a scientific basis. 

Whatever causes exist to prevent the operations of gardening 
from being carried out on scientific principles, it is nevertheless 
true, that no methods can be generally applicable, or universal 
in their results, that have not such principles for their bases. To 
be guided by them, it is not necessary that the gardener should 
be a mere reader of books, a studier of theories, or a continual 
performer of experiments ; he must add to the precepts of others 
the acquisitions of his own experience, and aim constantly at 
progress, by learning practically the principles upon which his 
operations rest for their success. It is not the lot of every one 
to discover truths hitherto unknown, but almost every one en- 
gaged in the practice of horticulture can do something towards 
improvement, by enforcing those already known by stronger 
evidence, facilitating them by a clearer method, and elucidating 
them by brighter illustrations. 

There is a wide-spread antipathy to all kinds of book instruc- 
tion, and book gardening is ridiculed by many who call them- 
selves gardeners. It is, nevertheless, a well ascertained fact, 
that those who rail at book practice are not only the worst prac- 
tical, but also the worst theorists, and the worst reasoners upon 
matters of practical import. Indeed, there are few who are more 
slow to recognize the benefits of the valuable knowledge to be 
found in the works of the eminent horticulturists of this country, 
than those by whom it is most required. 

Notwithstanding the valuable works which have lately been 
given to the world, on horticulture and the kindred arts, by 
eminent writers, little or nothing has been done in the depart- 
ment embraced by this treatise. Horticultural structures of all 
kinds continue to be made, and managed, with the same disre- 
gard to the actual habits and requirements of plants, as they 
were a century ago. And, though some structures of this kind 
have been constructed upon plans and principles in accordance 
with modern knowledge, yet these are a very small exception. 
Many apparently fine structures could be pointed to, which are 
rendered comparatively useless for the purposes for which they 



10 INTRODUCTION. 

were built, on account of a deficiency of knowledge on the part 
of those who superintended their erection. 

It is a common error for gardeners, and others, who erect 
glazed structures, to suppose that the kind of house perfectly- 
suitable in one place will be equally so in another ; or that the 
same arrangement answerable for one purpose will answer 
equally well for all purposes to which a glazed structure may 
be applied. Some of the consequences of these errors will be 
more particularly specified in a subsequent part of this work ; as 
also the external forms and internal arrangements which we 
have found most suitable to the different purposes. The influ- 
ence which a servile adherence to old methods has upon the 
progress of horticulture, is chiefly manifest to those who are 
most liable to be censured for innovations. Yet it is doubtful 
whether the odium incurred is not more than compensated by 
the pleasure which arises from the rewards of perseverance, by 
which we are enabled to abandon bad systems, as we gain more 
confidence in those that are tetter. 

It is said that practice is the best of all teachers ; that as our 
practice is lengthened, our experience is increased. However 
this axiom may hold good in the common affairs of life, it is 
frequently reversed among practical men, and years pass away 
without any enlargement of knowledge, or rectification of 
judgment. There are, indeed, many who never endeavor to 
improve, notwithstanding the opportunities which may be 
afforded them. The opinions they have received, and the 
practice they have learned, are seldom recalled for examination, 
and, having once supposed them to be right, they can never 
discover them to be erroneous. From this preconceived acqui- 
escence, few are entirely free ; from a dislike to apparently super- 
fluous labor, and from a fear of uncertain results, many stand 
still when they might go forward. 

Some may say, that if a practical man performs the operations 
which others have taught him, and succeeds as well as others 
have done r he does all that can be expected from him. But this 
is doing nothing for improvement, and very little for himself. 
It is every man's duty to endeavor to excel, both on account 
of his profession and of himself, as well as those who employ 



INTRODUCTION. 11 

him. It is easy to perceive that a gardener must not only know 
how to do, but have his reasons for doing. A man who continues 
to do his annual operations by mere routine, without knowing the 
foundation or reasons, cannot deviate from the narrow path in 
which he is confined, when any unexpected accident occurs. 

In the following treatise, we have endeavored to explain these 
principles, as far as they have been connected with the subjects 
upon which it treats, and to illustrate them in such a manner as 
to be easily understood by the general reader. 

The first part of the work we have devoted to the construction 
of Conservatories, Graperies, Green-houses, Pits, Frames, and 
every kind of horticultural buildings, giving the different posi- 
tions and aspects most suitable to each, and the various purposes 
for which particular structures are best adapted. We have also 
fully considered the different kinds of materials generally used 
in the erection of these buildings, and the respective merits of 
each. Glass, and its influences on vegetation, are also fully con- 
sidered and discussed in this part, — a subject which has hith- 
erto received very little attention from horticultural writers, but 
is nevertheless one of the most important items connected with 
exotic gardening. We have given the useful experiments of 
Mr. Hunt, on Light, and its effects on vegetation and germina- 
tion, and all other information which we have considered use- 
ful on this part of our subject. 

The second part embraces the most approved methods of 
heating horticultural structures, giving the principles of com- 
bustion and consumption of fuel, the prevention of smoke,, and 
the various volatile products of the coal ; the construction of 
flues and furnaces ; the different sizes and heating powers 
of pipes and boilers ; the circulation of water, and the pecu- 
liar modifications of apparatus suitable for particular struc- 
tures. We have given a considerable number of illustrations 
in this part, showing various methods of heating, with all of 
which we have had extensive practice, and some of them on 
entirely new principles. The various merits of hot air and 
hot water are considered on scientific as well as on practical 
grounds, and each acknowledged for what it is worth. 

The third part may be called the theory and practice of 
2 



12 INTRODUCTION. 

ventilation, including some valuable investigations of the phys- 
iological effects of the atmosphere, under different circumstances, 
and at different temperatures. Many of our remarks nave 
assumed a greater length than we originally intended, and if 
some appear repetitionary, this is in order to avoid, as much 
as possible, all strictly scientific technicalities and abstruse 
reasoning, whereby the minds of practical men are frequently 
unable to understand fully the end to which you direct them. 
We have added a section on the protection of horticultural 
structures in severe weather, — a subject which is worthy of 
much consideration. 

I may observe, that, in pointing out and freely comment- 
ing on principles and practices which are erroneous, but which 
have been practised and promulgated by others, it is under the 
impression that such errors, carrying with them, in general, 
some plausibility, have led, and may still lead, others to fall into 
similar mistakes. However invidious, therefore, be the task of 
pointing out these errors, it would be manifestly impossible to 
write on this subject without noticing them, and, if possible, 
pointing out the difference between right and wrong. This is the 
only apology which can be offered for the freedom with which 
some of the opinions and methods of others have been com- 
mented on in the various parts of this treatise. We have, how- 
ever, expatiated on them candidly, and in the true spirit of 
inquiry, pointing out the applicability of their principles and the 
utility of their practice. 

The different parts of the subject have been arranged under 
different heads, as far as has been practicable, in order that any 
of the different parts may be pursued intelligibly and clearly. 
In extenuation of any errors which may be found, we hope it 
will be considered that many of the points treated on are 
entirely new, and as yet undeveloped ; that no comprehensive 
view of the principles of exotic culture has yet been given. 
But we must not be understood to offer excuses for any errors, 
other than those that are embraced by this extenuating clause, 
which will be acknowledged if rectified in the true spirit of 
philosophical inquiry. • 



PART I. CONSTRUCTION OF 
HOT-HOUSES. 



SECTION I. 

SITUATION. 

1. Site and position. — Before proceeding to details regard- 
ing the structures themselves, it will be necessary to consider, 
briefly, the situation on which the structures are to stand. A 
glazed structure depends for its effect very much upon its posi- 
tion; and as the position most desirable for effect may very 
possibly militate against the utility and efficiency of the struc- 
ture, the question presents a double claim to our consideration. 
In illustrating the position most desirable for the erection of 
houses for horticultural purposes, I assume that the paramount 
object is utility. I will subsequently point out reasons which 
frequently occur to render the position of green-houses and con- 
servatories beyond the control of the erector. 

By site and position I must not be understood to imply merely 
the aspect upon which a house for horticultural purposes should 
stand. The aspect of a house may be affected by circumstances 
which have no relation to its site. In other words, the glazed 
elevations of a house may be turned in any direction, while the 
position may be altogether unsuitable whichever aspect may be 
given to it. The weather, at all seasons of the year, has unde- 
niably more influence on a house in some situations than it has 
upon houses in others more favorably placed ; and this influence 
is sensibly felt by the products which are grown within them. 



14 SITUATION. 

The climate, and especially the prevailing winds of the locality, 
should be studied attentively, in order to anticipate their changes, 
and avoid, as far as possible, their injurious effects. No doubt 
it is sometimes difficult to ascertain the precise spot on which to 
erect hot-houses, with these considerations in view, particularly 
when the ground is extensive and the choice limited ; yet, in 
most places, there are some spots preferable to others. A bleak, 
elevated position should never be chosen, if there be any choice 
left. If a bare, elevated spot must be chosen, either on account 
of there being no alternative, or from other adventitious consid- 
erations, such as to obtain a commanding view of the surround- 
ing country, or to present a more imposing appearance from the 
mansion, or from any other point of sight from which it may be 
thought desirable to view them, then the background should 
always be planted up with trees. This is indispensable, for two 
important reasons : — 

(1.) For shelter. The northern winds are cold and biting in 
frosty weather, and air can be admitted when the houses are 
well sheltered, when it otherwise would be impossible to do so 
without injury to the plants. Moreover, the north side of a 
horticultural structure of any kind is the only one that can be 
appropriately sheltered with tall growing trees. It is, there- 
fore, the more necessary that trees should be planted close 
enough to break the wind, but not so close that their overhang- 
ing branches, when they have attained their full size, may drip 
upon the glass. This last is an evil which ought, in all cases, 
to be avoided. Neither ought new houses to be placed so near 
trees, already standing on the grounds, that these circumstances 
may occur. 

(2.) For beauty and effect. I do not mean, in this paragraph, 
to allude to hot-houses in general as handsome architectural 
objects in the grounds of a country residence, — to which consider- 
ation I will subsequently allude, — but merely to the effect which 
hot-houses of the cheapest and plainest description may be easily 
made to produce, without much trouble or expense, or without 
adding one cent to the cost of the structure itself. Let any per- 
son take a glance at a structure of glass, or range of such struc- 
tures, having nothing but the distant sky for a background, and 



SITUATION. 15 

compare it with another, resting upon the green, glossy foliage 
of luxuriant trees towering above them, and these again reflect- 
ing their irregular outlines against the cloudless horizon behind 
them, and he cannot fail to be struck with the tame and spirit- 
less appearance of the former, and equally, also, by the pictur- 
esque and pleasing effect produced by the latter. 

A conservatory, or green-house, avowedly ornamental, and 
intended as an object of architectural beauty, or of individual 
elegance, requires the most exquisite taste and skill in harmo- 
nizing the objects around it. These surrounding objects, 
whether for utility or embellishment, may be so arranged as to 
heighten the effect of the whole, without impairing the individ- 
ual effect of the structure, or hiding any of its beauties. The 
various features of the structure should be presented to view 
from different points ; and if, from any walk or portion of the 
grounds, the structure present rather an unfavorable aspect, then 
some object should be interposed to obstruct the view from this 
particular point. When a walk is led along the skirt of a wood 
or plantation, where a glimmering of the structure is continu- 
ously visible from among the trees, the effect is bad, and ought, 
by all means, to be obviated by planting shrubbery and under- 
wood, leaving here and there an open vista through which a 
full view of the whole building, or portion of it, may be obtained. 

It has, for some time, been the rage in this country to place 
horticultural buildings of all kinds upon eminences, and sur- 
round them, either wholly or in front, with square terraces. 
These terraces are made sometimes of brick, in all its primi- 
tive redness, sometimes of small stones and mortar, and more 
frequently, perhaps, of grass, nearly perpendicular. It is gen- 
erally difficult to discover which is the most unnatural and 
unsightly ; and, in nineteen cases out of twenty, we have found 
the terrace itself, of whatever materials, of very questionable 
taste. Terraces grew out of necessity, — not out of taste, — 
except, perhaps, in the Dutch school, which an able writer on 
this subject styles " a double-distilled compound of labored 
symmetry, regularity, and stiffness." # A terrace may be in very 
good taste, in connection with a pretty little Tuscan or Italian 

* Downing's Landscape Gardening. 
2# 



16 



SITUATION. 



villa, when it is finished and ornamented as a terrace should 
be, i. e., with vases, urns, &c, of sizes and forms harmonizing 
properly with the architecture of the building. The same prin- 
ciple may be applied to detached conservatories when placed in 
the grounds as ornamental objects. 

While speaking of terraces, it may not be out of place to 
remark, that, about some of the finest gardens of this country, 
these grass walls are introduced to absolute satiety. Nothing- 
like a gentle, undulating surface is for a moment tolerated, but, 
as a matter of custom, the ground must be levelled, and flanked 
by a terrace. Now we think that when terraces are found neces- 
sary in front of a garden structure, of an ornamental charac- 
ter, they ought to be of a different character from those intermi- 
nable sod banks so liberally constructed about some fine places 
that we could mention, but forbear doing so, on the principle, 
that, where much has been done, a few errors in taste may be 
justified. However, it cannot be denied that a steep bank of 
grass, twelve or twenty feet deep and as many from the walls 
of the building, void of any architectural decoration or ornament 
of any description, save its own unrelieved formality, is in as 
bad taste as would be the surrounding of a mud-walled hut with 
architectural balustrades and sculptured ornaments. Steep, 
formal terraces, without architectural decorations to unite and 
harmonize them with the structure, are, unquestionably, the 
most insipid and meaningless objects that can be introduced 
into ornamental grounds. 

What is called an architectural terrace, consisting of a low 
parapet and balustrade of handsome masonry, or other rich 
ornamental work, has always a pleasing effect, especially when 
attached to buildings of an ornamental character,* whether 
these buildings be for dwellings, or for horticultural purposes. 
These terraces, however, are very different from those perpen- 
dicular turf-banks, of which I have already spoken. The 
former are truly artistical, and, in connection with classical 

* The reader who is interested in this subject, and wishes for further 
information on this kind of ornamental terraces, is referred to the ele- 
gant remarks and illustrations thereon by Mr. Downing. [See Do?vnmg's 
Landscape Gardening ; section, Architectural Embellishments.'] 



SITUATION. 17 

structures, constitute the harmonizing link between art in the 
building, and nature in the grounds. The latter are neither 
artistieal nor natural. 

Let the reader fancy to himself a horticultural structure, of 
unusually large dim< ituated on the southern declivity 

of an open field, without a single ^ r '<''^ leaf of foliage to inter- 
vene between the unbroken whiteness of the structure and the 
distant sky. The very ornaments of the building are altogether 
hidden, even at the distance of a dozen yard:-;, because their forms . 
are viewed upon a background of cloudless iracancyj directly in 
front is a terrace, more than a do/en feet deep, and so i teep as 
to require a ladder to scale it, and at the bottom it terminates 
with an abrupt angle, adjoining a potato and cabbage garden. 
However unquestionable may be the position of the splendid 
structure here referred to, there is something so irreconcilably 
incongruous about its precincts, that the most untutored imagi- 
nation IS at once Struck with the total want of harmony, unity, 
and effect. The terrace itself has the unfinished appearance 
of a dwelling-house, where the work has been suspended before 
the roof and chimneys hud been put on ; a thing appearing to 
have an isolated and independent existence, having no apparent 
relation either to the structure or the grounds, and heartily 
ed by both. Now the position of the building referred to 
is, undoubtedly, excellent, and a better site could not be found, 
to produce a more imposing effect from a front view, which, in 
horticultural structures, is generally the best, providing the 
structure be sufficiently elevated above the axis of vision. But 
in the present case the effect is destroyed : first, by a total want 
of unity and harmony in the foreground, and, secondly, by a want 
of the deep, dark foliage of trees, presenting their irregular 
outlines against the sky in the background, which gives <)\\ 
buildings, and more especially those of a light character, as hot- 
• ., &c, that picturesque and pleasing appearance, particu- 
larly when the surface of the ground is broken by undulations, 
and the scenery diversified with a variety of objects, distinct in 
themselves, yet harmonizing with each other. 

From the foregoing observations, the propriety will be seen 
of placing horticultural erections in the immediate vicinity of 



18 SITUATION. 

large trees, and of raising them where they do not already exist. 
A beautiful writer on this subject has observed, that green- 
houses in the country, without trees about them, are like ships 
divested of their masts and rigging, and impress the mind with 
the idea of their having wandered from their right position ; 
and, as Loudon justly remarks, a tree is the noblest object of 
inanimate nature, combining every species of beauty, from its 
sublime effect as a whole, to the most minute and refined ex- 
pression of the mind.^ We cannot too strongly urge the pro- 
priety of choosing a site where these advantages may be gained. 
This branch of landscape gardening has been already treated in 
a masterly manner by various writers ; therefore we consider it 
unnecessary to dwellany longer upon it. t 

The choice of position may, in some instances, be decided by 
other circumstances, such as an abundant supply of water. This 
is indispensable, in hot-houses of every description, though it 
seldom forms a very important consideration with architects, in 
their designs, who are perfectly unconscious of the amount of 
labor and expense subsequently created by a deficiency of this 
element. It is, therefore, desirable that the site chosen should 
command a plentiful supply of water, at all seasons of the year, 
independent of what may be collected from the roof. It should 
be considered that the period when the largest quantity of water 
is required for the use of the plants, is also the time when the 
supply from rains is scantiest and most precarious ; and though 
ample provision must be made for collecting all the water that 
falls upon the roof, into tanks and reservoirs, suitably and con- 
veniently placed for that purpose, yet this supply is not to be 
entirely relied upon ; and hence water ought to be conveyed by 
pipes, or some other means, from the nearest source, to supply 
the tanks when the rain-water is exhausted. 

Where a stream of water is commanded by the position of 

* Loudon's Encyclopedia of Gardening. 

f Those who wish to study the principles of landscape gardening, will 
find all that is requisite for their instruction and improvement in " Down- 
ing's Landscape Gardening," the only work we know wherein the prin- 
ciples of the art are treated in such a manner as to render them perfectly 
applicable to this country. 



SITUATION. 19 

the structure, it would be most desirable to convey it through 
the interior of the house, in a kind of rill, or small stream, run- 
ning through a shallow channel, or, what would be still better, 
to fall into a tank, over a small precipice, forming a little cas- 
cade, or water-fall. If the stream had sufficient power by its 
declivity, a small jet might be kept continually playing. In an 
ornamental plant structure, this would be the ne plus ultra of a 
water supply ; besides, the house would be kept delightfully 
cool in the hottest days of summer, and the rippling of the 
stream over the cascade, or the playing of the fountain, would 
prove the most agreeable music to the ear in the hot days of 
summer. 

We have here alluded to water, merely in so far as it may 
be likely to affect the choice of position. Of course, water may 
be supplied to a house by various other means, such as force 
pumps, and that admirable invention, the water-ram, by which 
jets, cascades, &c, may be also obtained ; but all these are at- 
tended with considerable expense, as well as subsequent labor, 
and, therefore, a natural, constant, and abundant supply of water, 
when possible, should not be abandoned, even at the expense of 
some trifling advantages in other respects. We have known 
places where the labor of carrying the water for the different 
departments of the exotic establishment during summer, exceeded 
the labor required to keep the garden in order.^ 

In regard to the precise elevation best suited for the site of 
horticultural buildings, various opinions exist ; some prefer low- 
lying grounds, others prefer a considerable altitude ; we have 
frequently seen both parties run into extremes. Low situations 
are generally warmer, and better sheltered from boisterous winds, 
which, however, is more than counterbalanced by certain evils 
consequent upon a very low site. In spring, low, swampy places 
are always subject to heavy depositions of dew and mist, which 
render them cold and damp, and expose vegetation of every 
description to be destroyed by vernal frosts, which is avoided in 
more elevated situations. We have this spring had abundant 
evidence of this fact, in a very large tree of the Platanus Occi- 

# For further information regarding cisterns and supplies of water, 
see Sec. IV. ; Internal Arrangements. 



20 



SITUATION. 



dentalis, which had its leaves entirely destroyed, after they 
were fully expanded, and are now strewed upon the grass be- 
neath. This tree, with various others that shared the same 
fate, stood in a low part of the pleasure ground, beside a lake. 
Trees of the same species, on higher ground, escaped without 
injury. 

We have invariably found, in our experience, that plant-houses 
situated in very low grounds, were cold and damp in winter, 
and hard upon the more tender kinds of plants. In summer, the 
atmosphere is generally stagnant and unhealthy, to plants as 
well as animals. If circumstances, therefore, afford any choice, 
very low situations should be avoided, as it is more easy, and 
certainly more profitable, to bring an elevated and airy situation 
into the condition desired, than it is to obviate the injurious 
effects of a low one. 

2. Aspect. — We find that most people prefer a southern 
aspect for their hot-houses, i. e., placing the front elevation due 
south. The absolute propriety of this preference, however, de- 
serves to be questioned, as experience has taught us that some 
valuable advantages are gained by placing hot-houses, for the 
growth of fruits, on a south-eastern aspect. Let it be observed, 
that we are alluding at present to what is termed lean-to, or 
shed-roofed houses, i. e., houses having only one sloping side, — a 
kind of structure still generally used for the production of grapes, 
&c, during the early part of spring, and which are probably 
better adapted for that purpose than span-roofed houses. In 
fact, we should prefer a south-eastern aspect for lean-to houses, 
whether they were intended to grow fruits or flowering plants ; 
for, even in this clear and comparatively cloudless climate, this 
aspect has advantages which, in our opinion, are not possessed 
by any other ; and, indeed, the greater intensity of the sun's rays 
at midday here than in England, gives this aspect greater ad- 
vantages in this country than in any other where the sun is less 
powerful. The morning sun is more strengthening and exhil- 
arating to plants than during any other period of the day, and 
more especially to plants kept in houses without artificial heat ; 
but the same argument holds good in all houses. We find that 



SITUATION. 21 

hot-houses, even during the early part of summer, — except fire 
heat be maintained, — sometimes fall exceedingly low at night, 
and become cold and chilly, with the aqueous vapors contained 
in the atmosphere, by the high temperature of the preceding 
day, condensed into water by the low temperature of the night, 
and depending in small globules from the leaves of the plants, 
the under surface of the glass, and other parts of the house, 
rendering the approach of the sun's cheering beams, a few 
hours earlier than if the house were" placed meridionally, above 
all things acceptable. 

It might be plausibly argued, that, if we take the south-east- 
ern aspect for the purpose of gaining the morning sun, we must 
lose it for the same period in the afternoon, which, altogether, 
makes it the same thing to the house. This is not true in prac- 
tice ; though the period of the sun's duration upon the house in 
both cases be the same, yet the advantage gained, by taking the 
morning and losing the afternoon sun, is very great. The rays 
thus lost in the evening are of little consequence compared 
with those gained in the morning, because the plants are then 
partially enfeebled, and their elaborative powers impaired, if not 
altogether suspended, by the strong midday heat. By various 
experiments on the shoots of young plants, we found that their 
elongation was greatest during the mild hours of the morning, 
before the sun had attained its meridian fierceness. 

In general, we find that plants are more prostrated by the in- 
fluence of the afternoon sun than during any other period of 
the day, and it is supposed, by many, that the sun's heat is more 
powerful and oppressive in the afternoon — that is to say, from 
one to three — than it is when on its meridian. However this 
fact may be scientifically supported, it certainly holds good in 
experience.^ Supposing, then, that such is the case, we con- 

* This may be accounted for by the air having been already -warmed 
to a high temperature, by the sun acting upon it during the previous 
part of the day ; and, the deposited moisture of the preceding night hav- 
ing been already evaporated from the surface of the earth, the lower 
strata are highly rarefied. The hot sun, continuing to act upon the lower 
stratum of air and the dry surface of earth, gives the former that lan- 
guid, oppressive, and suffocating character, which is experienced by 
every one. 



22 SITUATION. 

sider it another fact in favor of a south-eastern aspect, as the 
sun's rays will thus be made to strike the roof more obliquely, 
and will be less likely to scorch, or otherwise injure, the plants, 
than if shining- perpendicularly to the plane of the roof. 

Many authors might be quoted, in support of a south-eastern 
aspect ; and one of the best garden authors, of his own or any 
other time, says, " An open aspect to the east is a point of cap- 
ital importance, on account of the early sun." When the sun 
can reach the garden at its rising, continuing a regular and 
gradual influence, increasing as the day advances, it has a grad- 
ual and most beneficial effect in dissolving the hoar frost that 
may have been deposited the previous night. On the contrary, 
when the sun is excluded till about ten in the morning, and 
then suddenly darts upon it with all the force derived from its 
increased elevation, and increased power, it is very injurious, 
especially to fruit-bearing plants, in the spring months. The 
powerful rays of heat at once melt the icy particles, and, imme- 
diately acting upon the moisture thus created, scald the tender 
blossoms and leaves, which droop and fade as if nipped by a 
malignant blight.^ 

These remarks, it is true, are by an English author, and have 
reference to the climate of England ; but they apply to us in 
full force in this country, and, in many locations here, are still 
more applicable than to any country in Europe. 

The morning sun is not only more agreeable to vegetable as 
well as animal development, but, as we have already observed, 
vegetation proceeds more rapidly under its influence than it does 
during any other period of the day. This may be accounted 
for by the fact, that the nourishing gases have been accumu- 
lating during the partial suspension of elaboration in the night, 
and, on the approach of the sun's vivifying beams, these functions 
are resumed with increased activity, and continue so, under the 
mild influence of its less powerful and fierce effulgence, until 
their energies are paralyzed by its burning rays, at midday, when 
they make little more progress till the next morning. 

We have heard similar arguments adduced in favor of a south- 

* Abercrombie's Practical Gardener. 



SITUATION. 23 

western aspect for late houses, and these facts have regulated 
the erection of some extensive houses with which we are ac- 
quainted. In this country, however, hot-houses are seldom 
erected for the express purpose of retarding grapes, or other 
fruits, although we have no doubt that very late grapes would 
pay better than early ones, since there would be very little ex- 
pense in their production. The sun's rays in this climate are 
so powerful, that the difference in aspect may not be so percep- 
tible, in regard to late and early forcing, as in England ; still 
we have no doubt the difference will be found sufficient to justify 
the erection of houses for these purposes, on the aspects we have 
pointed out as being most suitable for each. 

In the erection of span-roofed houses, that is, houses with 
double roofs, it makes very little difference, in the opinion of 
many, which way the house may stand, and, upon the whole, 
the arguments hitherto used, in favor of one aspect over another, 
have been so feeble as hardly to deserve any consideration. 
Supposing the house to be a parallelogram, or long square, with 
both gables glazed, as well as the sides and roof, then, we think, 
it may stand any way in which the nature of the site, or taste 
of the erector, may dictate. Light being the most important 
point of attention in the construction of hot-houses, these are 
better adapted for plant-growing than those whose transparent 
surface forms only a segment of their transverse section. 

As a general principle, provided other circumstances are fa- 
vorable, we would recommend the house to stand north and south, 
with its longer elevations towards the east and west ; we find 
this to be the opinion of some of the best gardeners in the coun- 
try, with which we fully agree. If any advantage be, gained by 
placing the house in one direction, in preference to another, we 
think it is the one mentioned, as the rays of the meridian sun 
will then strike the glass in an oblique direction, and have less 
power than if they were to fall upon the glass at right angles 
to it.^ 

The aspect of conservatories attached to dwelling-houses 

* For more detailed information on this matter, see Sec. II., Design 
and Slope of Roof. 
3 



24 SITUATION. 

must be regulated by the position of the building, or the fancy 
of the architect. These are deplorable erections, generally; 
nine tenths of them unsuitable, in the superlative degree, not 
for want of cost, but for want of skill. As the remarks we have 
to make, on this part of our subject, belong to the next sec- 
tion, we will just add here, that a conservatory ought never 
to be placed on the northern aspect of a building, nor situated 
in such a manner, in relation to the dwelling-house, that the 
sun's rays may be prevented from falling on the conservatory 
during at least one half the day. 






SECTION II. 

DESIGN. 

1. General Principles. — To ascertain principles of action, 
it is always necessary to begin by considering the end in view. 
The object or end of hot-houses is to form habitations for vege- 
tables, and either for such exotic plants as will not grow in the 
open air of the country where the structure is to be erected, or 
for such indigenous or acclimated plants as it is desired to force 
or excite into a state of vegetation, or accelerate in their pro- 
gress to maturity, at extraordinary seasons. The former class 
of structures are generally denominated green-houses, or botanic 
stoves, in which the object is to imitate the native clime and 
soil of the plants cultivated; the latter, comprehending forcing- 
houses and culinary stoves, in which the object is to form an 
exciting climate and soil on general principles, and to imitate 
particular climates. 

The chief agents of vegetable growth in their natural habita- 
tions are light, heat, air, soil, and moisture; and the merit of 
managing these structures, and the success of cultivating vege- 
tables in them, depend on the perfection with which nature in 
these respects is imitated. 

To cany* out the imitation to perfection, or anything like an 
approach to it, it is absolutely necessary, as we have previously 
observed, to be acquainted with the nature and habits of the 
plants under cultivation. Vegetable physiology ought to form a 
part of the acquirements of the hot-house architect; and the 
chief cause of the great improvement in these structures, of late 
years, in England, is traceable to the fact, that their erection is 
no longer left, as formerly, under the control of mansion archi- 
tects, as they are at the present day throughout the length and 



db DESIGN. 

breadth of the United States ; and the chief reason why we see 
horticultural structures erected so numerously in this country, 
in violation of the first principles of plant- culture, is undoubt- 
edly due to the same cause. The conservatory is generally left 
to the uncontrolled management of the architect, who, of course, 
makes this structure to correspond with the rest of the building, 
without giving the slightest consideration to the vegetable beings 
that are to grow in it If we consider this matter in its dif- 
ferent bearings, giving to professional architects the justice 
which is due them, it would be somewhat unreasonable to 
expect them to plan conservatories otherwise. An architect is, 
by education, taught to study and apply principles in his art, 
which, when carried into effect, as we sometimes see them in 
the construction of plant-houses, are in direct opposition to those 
laws which nature has laid down and determined as essential 
to the vigorous development of vegetable life. Can it be 
expected, then, that an architect will tamely surrender the grand 
principles of his art, — the antiquity of which is coeval with 
Cheops, and which has been the boast and pride of the greatest 
empires of the old world, — in meek submission before the yet 
half-developed principles of vegetable physiology, or even to the 
humble dictates of practical gardening ? To expect such a con- 
cession would be tantamount to expecting an architect to build 
dwelling-houses with drawing-rooms solely adapted for the 
accommodation of plants, altogether irrespective of other pur- 
poses to which drawing-rooms are generally applied. Hence, 
we find the conservatory placed just where it is most subservi- 
ent to the general design of the mansion, most frequently in a 
corner or recess of the main building, having two or three sides 
of solid opaque material ! To civil architecture, as far as 
respects mechanical principles, or the laws of the strength and 
durability of materials, they are certainly subject, in common 
with every other species or description of edifice ; but in respect 
to the principles of design and beauty, the foundation of which 
we consider, in works of utility at least, to be " fitness for the 
end in view," they are no more subject to the rules of civil archi- 
tecture than is a ship or a fortress ; for those forms and combi- 
nations of forms, and that composition of building, which is 



_ L. - ~: . 



m 



rer~ i:::i:-. i-i- iimis :ir::j";'. 11 :-. ii:ii:::i ::: 1121 :: 
for domestic animals, is by no means fitting, and consequently 
not beautiful, in a habitation for plants. Such, however, is the 
force of habit and professional bias, that it is not easy to con- 

t— :e i::h:t::5 ::' :i:s :n:'i Sninirii :'•:■: 111115 ir-= ::: ti- 
ered by them no further beautiful than as they display some- 

LLinr .: ' i: :i::i::iii. :::ns - 111 . 1: : :::::..- :<: 111 11:1 "i 

iiiiiniii: Ut — 1:11 :: 15. ::i=ii: ::' 1 s:li: :.:-.'.-'t iiilinr 
for it is an undeniable iact that what are called fine architecto- 
nl consenatories, are designed, not for the porposT : : gi ~~ing or 
T;3n::::nr i:~ 11 z " :•:: *..-;' : .: "-. -'-'. r" . ::.r ipi^r- 

e ::' 1111111:11 :':: :L:= : r :— Jit in :■:" -iri 
■ .: !:•= 1= : is: lire : it .. -t . ■ . ::.--.. 
r.ms 111:11-1 : :::ii:.i: 7. — 1:: :': :n_ 111 n :•;::-..:_.: ss 
ibrms only a small fraction of the surface ostensibly appropriated 
to the transmission of light. To complete the opacity of the 
■:::::r 111 — ::'.: L: : isiiLri: . :: :i::t: ::- 1:.: :_t . 

i_in ; ;.: in Tieri 1= 1: It: -::,7t::- :: 1 :::: ney 

:"::::. m pi: rill .:. :^m-i:i". : :i:t" n::.!: :-..:i iie 

Tiiry ::i 1:1 :"i~ It: :-: ::ie ::: Tiii:^: :ie .-:. . : ::i- 

serratory erected by J. W ?:i ■ Esq it his mansion at Brook- 

7:i: 111 iriiTi 11 I:~ii- L11: 

1 T-"i::i 7 Til. t: : . :: .-. 1: i_t ...: 1 \-: : 1 t :> 

1 .: it. irr : 11 ---_ :_ = 111 :h:t1 :: i:t : : 1 .: .. 

t \-.\ .-. :';. ni : t: ::::i: ::: 111 

It: :: — — t :: 1 : .".. : : 1 > Ye: "iniiii. 11 1 1: : s :: 

:::: . tt: ItIt iet-: ~i: :::. i"i:"../i 1: . 

11 :: :: ienV.:::i 1:: 1 : ::-.:tt . " 1:1 in: ::' 1:1 :: 

5^1 -: :: :: :i ::::. : jirnin- 



: : 1 1 : 1 1 1 ne 
111 :i: 111:11 i::ii 11 1:1: in i_::i:~"i: 
~^ are — ell 1:11111:11 -~:i :n sm:nr= itself 1: ~e_ 
3* 



28 DESIGN. 

as with the able and excellent gardener who has managed it for 
many years, and who finds it impossible to grow plants within, 
and has long since given up the case as utterly hopeless ; the 
only result which could be expected. 

It may seem strange that ten or twelve thousand dollars 
should be expended upon a plant-house, and, after all the 
expense, the house be unfit for the growth of plants, and that 
this fitness could be more extensively obtained at one twentieth 
the cost. Such, however, is the case, and will continue to be 
so, till the design be considered in relation to " fitness for the 
end in view;" and that this is far from being the case, we have 
lately experienced sufficient proof. Buildings like that we have 
just alluded to, may properly be called beautiful specimens of 
architecture, but if the principles of design or beauty be regarded 
on fitness for the end in view, — as we believe it to be in works 
of utility, — then, as plant-conservatories, these structures ought 
to be condemned. 

I have no doubt some of our architectural readers, and lovers 
of dull, massive, gorgeous, and grotesque conservatories, will 
pronounce against such a violation of the principles of architec- 
ture, as would undoubtedly be perpetrated by building a mere 
shell of glass to form a counterpart of the solid masonry of a 
large mansion. Conversing on this point lately with a talented 
architect, he said, " Conservatories can never be reconciled with 
mansion architecture if they must be erected upon such princi- 
ples ; the thing is utterly inconsistent with beauty in a building. 
Such an appendage," said he, " would be as absurd as putting a 
gauze covering over a buffalo robe to withstand a snow storm." 
It would be useless here to reply to the injustice and inapplica- 
bility of these observations, and we will let them go for what 
they are worth. They serve, however, to convey a pretty accu- 
rate idea of the estimation in which architects hold the principles 
of plant culture, even when pointed out to them; or, as we might 
term it, how little they care for the beauty expressed by " fitness 
of purpose." Utility, however, is undoubtedly the basis of all 
beauty in works of use, and, therefore, the taste of architects, so 
applied, may safely be pronounced as radically wrong. 



DESIGN. 29 

2. Light. — In erecting horticultural structures of any 
description, the first and decidedly the most important object to 
be kept in view, is the introduction of light ; and really, though 
this point presents itself to architects in its simplest and plainest 
reality, it appears to be scarcely ever fully considered ; at least, 
we are induced to conclude so, from the instances already before 
us. It is easy for any person to satisfy himself of the wonder- 
ful effects of light upon vegetables under artificial culture, by 
the most familiar illustrations. When plants are placed against 
a wall, or other opaque body, they will speedily turn the sur- 
face of their leaves to the light, although the medium of its 
entrance should be many yards distant. One of the principal 
reasons why plants thrive so badly in dwelling-houses, is in 
consequence of their being deprived of that supply of light 
which is essential to their development. Set a plant how or 
where you will, it will twist and turn itself in any direction for 
the purpose of presenting its leaves to the light, or to the aper- 
ture where it enters unobstructed. Pure air is also a most essen- 
tial element in the economy of vegetation ; but we may safely 
assert, after much experience, that plants under artificial culture 
suffer far more from a deficiency of light than from a deficiency 
of what is called pure air. The reason of this appears obvious. 
By the latter deficiency a plant is merely deprived of its neces- 
sary food ; but by the former deficiency the plant is entirely 
deprived of its vegetable functions, or its energies are so en- 
feebled as to be incapable of assimilation. We are not speaking 
here of light merely as distinguished from darkness, for we are 
told, upon good authority, that the luminiferous ether is radiated 
in all directions from its grand source, viz., the sun,^ but of 
its properties and influence on plants when transmitted through 
a transparent medium, such as glass. Every gardener knows 
that plants will not only fail to thrive without much light, but 
will not thrive unless they receive its direct influence by being 
placed near the glass. The cause of this last fact has never 
been satisfactorily explained. It seems probable that the glass, 

* Principles of Chemistry, by Prof. Silliman, Jr. 



30 DESIGN. 

acting in some degree like the triangular prism, partially decom- 
poses or deranges the order of the rays. 

The theory of the transmission of light through transparent 
bodies is derived from the well-known law in optics, that the 
influence of the sun's rays on any surface, both in respect to 
light and heat, is directly as the sine of the sun's altitude, 
or, in other words, directly as its perpendicularity to that sur- 
face. If the surface is transparent, the number of rays which 
pass through the substance is governed by the same laws. 
Thus, if one thousand rays fall perpendicularly upon a surface 
of the best crown glass, the whole will pass through, excepting 
about a fortieth part, which the impurities of even the finest 
crystal, according to Bouquer, will exclude. But if these rays 
fall at an incidental angle of 75°, two hundred and ninety-nine 
rays, according to the same author, will be reflected. The inci- 
dental angle, it will be recollected, is that contained between the 
plane of the falling or impinging ray and a perpendicular to 
the surface on which it falls.^ 

In building a green-house or conservatory, then, light ought 
to form the first point of importance, as success in plant culture 
is entirely subservient to it, and we know full well, from experi- 
ence, that no skill, however perfect, and no attention, however 
zealous, will compensate for a deficiency of light. Indeed, no 
contingent or permanent advantage can justify, to the mind of 
the experienced gardener, the adoption of one inch of opaque 
material in the sides and roof of a horticultural building; and 
no part of the structure, from the side-shelves and upwards, 
should be rendered opaque that can consistently be covered with 
a material capable of admitting the rays of light. For pillars 
and other appendages of strength, the material ought to be as 
light as is consistent with strength and durability in the struc- 
ture ; and, although we do not recommend such an erection 
adjoining a dwelling-house, experience has taught that, both in 
this country and in others, a mere shell of glass, so to speak, is 
not only the cheapest, but also the best adapted for the artificial 
culture of all kinds of plants, both for fruiting and flowering; 

*See Inclination of Hot-house Roofs. 



31 



t. t, : : :ultivatfe: 

The ^2iact manner in which 
studied by Dr. Dan 

Cl:;:-.:.^. ::' Airi.: l*::i 1545 J oring - . Ssi Da : 

I . . i ooljr three 

i . i t lue . 

- 

t - : . : ...... 

. - . : : • : 

....... . - - ...:._. 

. " - 

: - . . . : . 

. . '. . . : . 

: . . \ '. .-. . . . . 

.:.... . . ... . [ : 

... .... . . : . - 

: . . . '..:.:;•'.. 

. : ;. ;.;i:_e ::'::. . : . e 

. : . . . ./.:■-.■.. 

: I : . .-. .-.-.... V . . : '. . ..:..• 

. . . : L Or S . . . . . . ; 

: : . 

..... . .:.... ..;..-. 

..-..'. 1 . ' : . ... . : 

....... : . - : _ _ ■ .' : . ..... . 

. '. . E 1 1 ; v.." - -. f .-; . r. . L . . — 

3 . . .;..:. : . : . 

. . . . .:::.:. . . . E 

;:.t.:t: :i= " . . .g ;_:.: b;-;i \~: \. Tie germicatioD 

: : . . . . ... . . : 

: . ...... 



6"Z DESIGN. 

ous to the early stages of vegetation, Mr. Hunt believes that, 
in the more advanced periods of growth, they become essential 
to the formation of woody fibre. 

(2.) Light which has permeated red media. Heat rays. — 
Germination, — if the seeds are very carefully watered, and a 
sufficient quantity of water is added to supply the deficiency of 
the increased evaporation, — will take place here. The plant is 
not, however, of a health}'' character, and, generally speaking, 
the leaves are partially blanched, showing that the production 
of chlorophyl i-s prevented. Most plants, instead of bending 
towards red light, as they do towards white light, bend from it 
in a very remarkable manner. Plants, in a flowering condition, 
may be preserved for a much longer time, under the influence 
of red, than under any other media ; and Mr. Hunt thinks 
that red media are highly beneficial under the fruiting process. 

(3.) Light which has permeated blue media. Chemical rays. 
— The rays thus separated from the heat and light rays, and 
which Mr. Hunt has proposed to call Actimic, have the power 
of accelerating, in a remarkable manner, the germination of seeds, 
and the growth of the young plant. After a certain period, vary- 
ing with nearly every plant upon which experiments have been 
made, these rays become too stimulating, and growth proceeds 
rapidly, without the necessary strength. The removal of the 
plant into yellow rays, or into light which has penetrated an 
emerald green glass, accelerates the deposition of carbon, and 
the consequent formation of woody fibre. It was also found 
that, under the concentrated actimic force, seeds will germinate 
beneath the soil, at a depth in which they would not have grown 
under natural conditions. Mr. Hunt believes that the germina- 
tion of seeds in the spring, the flowering of plants in summer, 
and the ripening of fruits in autumn, are dependent upon the 
variations in the amount of actimism, or chemical influence, of 
light and heat in the solar beam at these seasons. 

It must, however, be observed, that, although such experiments 
have much physiological interest, the value of them is greatly 
diminished by the necessarily imperfect manner in which the 
prismatic colors are separated by artificial preparations. It is 



DESIGN. 33 

almost, if not quite, impossible to form pure colors artificially. 
The yellow, for instance, of the bichromate of potass contains 
both red and violet in abundance.^ 

It has been already ascertained that the amount of assimila- 
tion, and consequently of the healthy exercise of its vital func- 
tions, depend upon the intensity of the light to- which the plant 
is exposed. In bright sunshine they perspire most; in weak 
diffused light, and in darkness, none at all. Hales found that a 
cabbage lost nineteen ounces of weight per diem, and a sunflower 
twenty. He estimated the average rate of perspiration by plants 
to be equal to seventeen times that of a man. In one of his exper- 
iments he found that the branch of an apple-tree, two feet long, 
with twenty apples, exposed to bright sunshine, raised a column 
of mercury twelve inches in seven minutes. But a dry, arid 
atmosphere, especially if in motion, also robs the plants of their 
moisture independently of light. 

The clear and unclouded skies of this country do not, as some 
suppose, obviate the necessity of surrounding the plant with a 
transparent medium in all directions, nor does the dark and sun- 
less climate of England render it necessary that the houses 
should be more transparent there than here. It is a practical 
absurdity to fancy that in England there is less light than in 
this country, and that, because the mid-day sun is more powerful, 
they can do with a greater opacity of structure. Those who 
make such statements manifestly know as little of the climate 
of England as of the natures of its skies, and mislead those who 
know as little as themselves. No argument whatever, based 
upon the brightness of the sunshine at mid-day, can serve to 
justify the adoption of one single inch of opaque material in a 
horticultural building. It is very easy to reduce the quantity of 
light, or break the rays of the sunshine, by shading; but it is not 
so easy to increase the quantity of light in the dark and gloomy 
months of winter ; and such sort of plant-houses will damp the 
energies and zeal of the most skilful gardener, as well as his 
tender exotics. When he sees these errors, which he cannot 
remedy, and observes his plants speaking in a language which 

* For further experiments on Light, see Sect. IV., Glass. 



34 DESIGN. 

cannot be mistaken, even by the most inattentive, " Give us light, 
or we shall die ! " he gives up their case, in hopeless despair, as 
being altogether beyond his control. And thus we have known 
excellent gardeners censured for neglecting things, and for doing 
badly what it was not in their power to do better. 

Solar influence being necessarily connected with the roofs of 
hot-houses, we will discuss these subjects in their relation to 
each other, including inclination and reflection, in the following 
sub-section. 

3. Slope of hot-house roofs. — In regard to the theory of the 
transmission of light through transparent bodies, we have already 
stated that the influence of the sun's rays on any surface is 
directly as his perpendicularity is to that surface ; and, accord- 
ing to Bouquer, that if one thousand rays fall perpendicularly 
upon a surface of glass, the whole pass through, excepting about 
twenty-five rays, or one fortieth part of the whole. But falling 
on the same surface at an incidental angle of about 75°, then 
two hundred and ninety-nine, or nearly one third of them, will 
be reflected. The influence of the sun on the roofs of hot-houses 
depends very much on the principle there given, — at least, so 
far as regards the form of its surface. This principle has been 
applied, in various ways, for the purpose of obtaining the full 
influence of the sun's rays at certain seasons of the year. We 
have managed forcing-houses where the roof was laid at right 
angles to the sun's rays in mid-winter, — the period when the 
most powerful rays were required for forcing purposes. 

Although it cannot be denied that much more depends on the 
management of the house, for the success of cultivation, than on 
the inclination of the roof, yet it is the most satisfactory method 
to proceed on what may be considered something like princi- 
ples.. And in this country we find this the more necessary, 
because the heat of the sun's rays, at certain seasons of the year, 
is so violent as to prove injurious to vegetation under any cir- 
cumstances. And hence, this principle should be adopted in the 
construction of hot-house roofs, that their perpendicularity to the 
sun's rays, at the hottest period of the year, should by all means 
be avoided* 



DESIGN. 



35 



In England, the most common elevation of roof is an angle of 
45°, which, in the latitude of London, would form a perpendic- 
ular to the impinging ray, about the beginning of April, and the 
beginning of September, — which also makes the obliquity of 
the rays greatest when they are most powerful, viz., during the 
month of June. " This angle is preferred by most gardeners," 
observes Loudon, " probably from habit." We think, however, 
that something more than mere habit justifies the adoption of 
this angle, — more especially for forcing-houses, — since by it 
the benefit of perpendicularity is obtained at a period when the 
rays are comparatively feeble and most necessary. 

Fig. 1. 









Y 


\e 




,••/ 






\c 




.«•"" V 








s& 




V 








X.a 


/ 




^ 

^^^ 




w\ 







As some of our readers may not have made themselves suffi- 
ciently acquainted with the altitude of the sun in relation to the 
slope of hot-house roofs, we have annexed the above figure, 
(Fig. 1,) which represents the slope of five different roofs on the 
angles marked by their respective complements, /represents 
4 



3b DESIGN. 

the altitude of the sun in the latitude of London, the impinging 
ray falling on the roof, c, at an angle of 45°. It will be seen 
that the angle, contained between the back wall of the house 
and the inclined plane of the roof, c, is just equal to the sun's 
altitude, — the one forming an exact perpendicular to the other. 
Allowing, then, for the difference of altitude betwixt the 
latitudes of London and Philadelphia, for instance, we have a 
difference of inclination of about 11°. Hence the roof of a hot- 
house, to receive the same influence of the sun's rays at that 
period, would be at an angle of 34°. The difference will be 
more closely perceived by the following cut. 

Fig. 2. 




In this cut we have given the altitude of the sun at Philadel- 
phia, a, with the roof at right angles to it, on an angle of 34°. 
At b, we have given the altitude of the sun at London, with its 
corresponding angle of elevation, 45°, and, according to the 
principle here laid down, both of these roofs should be equally 
influenced by the sun, notwithstanding the difference of his 
altitude at the respective places. 

In a theoretical point of view these principles are correct, and 
are certainly preferable to the usual mode of putting on roofs 



DESIGN. 37 

without regard to anything excepting the caprice or fancy of the 
architect or builder. But, as general principles, we regard them 
as unsafe and dangerous, were they to be practically acted upon 
in the Southern States. Suppose, for instance, the roof should 
be laid at right angles to the sun in mid-summer, — as is some- 
times done in England, upon this principle, — then the conse- 
quence would be that his rays would be unendurable by any 
species of vegetation. The mid-summer sun, even in the lati- 
tude of Baltimore, (39° 45',) falling on a transparent surface, 
at right angles to the impinging rays, would scorch vegetable 
forms, and dry them up in a few hours. 

It is, therefore, absolutely necessary that the exercise of this 
principle be limited to northern latitudes, where it is indispensa- 
ble to economize the sun's heat, for the purpose of accelerating 
the maturation of fruits. It may, also, be applied in more 
southern latitudes, when all the warmth of the sun's rays is 
required early in spring ; and, therefore, if the principle be 
applied south of the 40° of latitude, it should be taken when 
the sun is at its very lowest altitude, -otherwise the pitch of the 
roof will be too flat for the months of summer. 

We are decidedly of opinion — and this opinion is fully con- 
curred in by some of the most learned and skilful gardeners in 
the country — that a great deal of error is committed in the 
pitch of hot-house roofs; probably more than four fifths of them 
are made too flat ; their angles of elevation are much too small 
for the climate ; and yet, notwithstanding the fierce heat of our 
perpendicular sun in summer, this practice is daily persisted in. 
One would suppose that the scorching of vine-leaves, peaches, 
and other plants, would convince people of the impropriety of 
erecting their hot-house roofs at right angles to the sun's rays 
in any of the summer months ; and yet we know some of the 
finest graperies in this country on angles of about 20°. If we 
consider how very few of the rays are reflected by the glass, as 
its plane approaches a perpendicular to the sun's altitude, and 
how many are reflected as the angle of incidence is increased, 
we will then have some notion of the advantage of increasing 
the obliquity of the roof. 

The annexed table will show the number of rays reflected 



38 



DESIGN. 



from various angles between the plane of the horizon, and within 
two and a half degrees of the perpendicular. 

Bouguerh Table of Rays reflected from Glass. 
Of 1000 incidental rays, when the angle of incidence is 



87° 30', . . 


. . .584 are 


reflected. 


60°, . . . 


... 112 are 


reflected. 


85°, . . . 


. . .543 " 


it 


50°, . . . 


... 57 " 


a 


82° 30', . . 


. . .474 « 


te 


40 D , . . . 


... 34 " 


it 


80°, . . . 


. . .412 " 


it 


30°, . . . 


... 27 " 


it 


77° 30', . . 


. . .356 " 


ti 


20°, . . . 


... 25 " 


u 


75°, . . . 


. . .299 « 


(C 


10°, . . . 


. . . 25 " 


Cl 


70°, . . . 


. . .222 " 


ti 


1°, . . . 


... 25 « 


11 


65°, . . . 


. . . 175 " 


a 









The slope of hot-house roofs, therefore, should depend on the 
following circumstances : 

The latitude under which they are erected. — If in a southern 
latitude, the plane of the roof should be as oblique as possible 
to the sun's rays. South of 40°, the angle of incidence should 
not be less than 20°. It will be recollected that this angle is 
contained between the sun's rays and a perpendicular to the 
roof. 

The position of the house, and the purposes for which it is 
intended. — Houses intended for the forcing of fruits in winter, 
may have their roofs made on a perpendicular to the sun's rays 
at that season. Conservatories attached to dwelling-houses may 
also have their roofs perpendicular to the rays of the winter sun, 
for the same purpose ; but blinds should be provided for them, 
during the months of summer, to guard against the effects of 
the perpendicular rays when the sun is crossing his meridian 
altitude, 



SECTION III. 

STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

1. Forcing-houses, culinary houses, fyc. — Forcing-houses are 
erected with the intention of forming an artificial climate for 
the culture of tender plants and vegetables in winter and early 
spring. For this purpose artificial heat is employed to keep up 
an exciting temperature, and, therefore, it is desirable that they 
should be constructed in relation to this end. 

Until very lately, the form in which forcing-houses were con- 
structed was that of lean-to, or single-roofed, houses, with sheds 
or garden-offices on the back of them. When it is not neces- 
sary that light should be received from all sides of the house, 
these lean-to houses answer very well, and possess many con- 
veniences which cannot be obtained with span-roofs. Climbing 
plants, such as grape-vines, trained beneath the glass, and 
peaches, trained in the same manner, derive a sufficiency of 
light from the single roof to enable them to bring their fruit to 
perfection ; and it is very doubtful if single roofs will ever be 
entirely superseded for the purposes of winter forcing. 

Fig. 3. 

JX 




Fig. 3 is the section of a pit for winter forcing, which we 
consider well fitted for the several purposes to which these pits 



40 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

may be applied. The one here represented is what we have 
formerly used for the culture of grape vines, French beans, and 
strawberries, during winter ; and where fermenting manure is to 
be had in abundance, it is probably the most economical house 
for this kind of forcing. 

Fig. 4 is the plan of a forcing pit. This house is 80 feet long, 
in two divisions of 40 feet each. It is chiefly intended for forc- 
ing vines in pots, and is furnished with a bed, b, which is filled 
with fermenting materials for plunging the vines in, and supplying 
them with bottom heat. A shelf, c, elevated to within about 20 
inches of the glass, on the back wall, and extending the whole 
length of the house, is intended for forcing strawberries in pots ; 
d is another shelf, for the same purpose, on the front wall. 

We have designed this pit with the view to procure the great- 
est accommodation in the given space, at the smallest expenditure 
for construction, keeping strictly in view the purposes for which 
it is intended. For winter forcing, we decidedly approve of this 
kind of house above all others, i. e., where utility only is consid- 
ered in regard to it. The cost of this house is only four hundred 
dollars, or eight dollars per linear foot. 

A house for winter forcing should never exceed 40 feet in 
length, even where the operations are extensive. Thirty or 35 
feet is considered, by the best gardeners, the most desirable 
length. If the range be a greater length, and the operations 
very extensive, it should be subdivided into either of the dimen- 
sions here stated, and each division heated by a separate appara- 
tus. 

There is no branch of gardening that requires a greater amount 
of skill, or is more calculated to display the mastership of the 
gardener's art, than winter forcing. It is absolute folly for any 
novice in gardening to attempt it. To be successful in produc- 
ing the luxuries of summer, in winter or early spring, requires a 
great degree of skill, vigilance, constant and persevering energy. 
The most unwearied attention is requisite, from the day the 
house is started into work, until the productions are all fully 
matured. Scarcely a day passes but something happens, tend- 
ing to thwart the object of our labors. Heat or cold, wind or 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 41 




42 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



steam, moisture and drought, mice, worms, slugs, aphides, and 
insects innumerable, as Cowper says, oft work dire disappoint- 
ment, that admits no cure, and which no care can obviate. It 
is, therefore, the more requisite that the structure intended for 
these purposes should be the best that science and practice can 
adopt. 

Fig. 5 is the end section of a forcing-stove, which we have 
seen used in various parts of this country, with considerable suc- 
cess. It is sunk a few feet into the ground, so that the roof 
reaches within about two feet of the ground level. In some 
places this kind of pit answers very well, as in very dry and 
sheltered situations. • The site of such a pit must necessarily be 
in gravel, or sand; in wet clay, coldness and dampness would be 
unavoidable ; and in exposed situations, it would be very unsuit- 
able for winter forcing, unless provision were made for covering 
it at night. 

Fig. 5. 




Fig. 6 shows the end section of a polyprosopic forcing-house, 
which, by some, is considered superior to all other forms for 
winter forcing. The roof presents the different faces to the sun's 
rays, a, a, a, at different periods of the year. This kind of roof 
may be considered as exactly equivalent to a curvilinear figure, 
whose curved lines shall touch all the angles of the faces, so that, 
were the house built in the form of a semi-ellipse, or having 
curved ends, the .sun would be nearly perpendicular to some one 
of the faces every hour of the day, and every day in the year. 

The rafters in this house are curved the same as in a curvi- 



Fie. 6. 














. 



44 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

linear house, and should be made of iron, as a curvature for this 
purpose can be made cheaper of iron than of wood, and is 
tighter and more durable. Iron beams are made to screw into 
the rafters, b, b, b, b, having- a fillet in which the smaller rafters 
are placed, on which the sashes run. We have seen two methods 
of constructing this kind of roof, — the one just described, in 
which the sashes are made to slide, and another, in which the 
sashes are made to rise on hinges, by which the house may be 
aired, over the whole surface of the roof, or entirely exposed, for 
admission of a congenial shower of rain, or for hardening the 
vines or peach trees, after the crop has been gathered. The 
arrangement by which this is effected is exceedingly simple, not 
liable to get out of repair, and is applicable to all kinds of houses, 
whether the roof is formed of curved or straight lines. This 
form of house is considered by Loudon as the ne plus ultra of 
improvement, so far as air and light are concerned. We are of 
opinion, however, that these considerations alone render it less 
valuable in this country than it is in England, except, as we 
have already stated, for the purposes of winter forcing. 

The Cambridge pit, Fig. 7, is admirably adapted for early 
forcing, where there is an abundant supply of stable manure. 
It is heated entirely with fermenting material, and is much used 
in England for the purpose of growing pine-apples, melons, 
cucumbers, &c. <z, a, are shutters, which lift entirely off, or are 
wrought up and down by hinges attached to the back wall of 
the pit. These shutters are made to fit closely on the lining 
bed, b, b, which is kept constantly filled with the materials to 
supply the heat, which enters the interior of the pit through 
pigeon-holes in the wall. We have kept pines during long and 
severe winters, in this kind of pit, keeping up a temperature of 
50° to 55° in the coldest weather. During winter the linings 
require to be frequently renewed, at least every week some fresh 
material must be added, otherwise the heat will decline below 
the minimum temperature ; and, as it will be some time before 
the new linings generate much heat, a part should only be re- 
newed at one time, and never both sides of the pit at once. 

Saunders' forcing-pit, Fig. 8, is considered an improvement 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 45 

upon the foregoing. This pit has a double roof, and is furnished 
with the dung-beds, #, a, on each side of the house. The fer- 
menting material is supplied by means of linings along both 
sides of the pit, and communicates the heat to the beds through 
the arches in the side walls. This pit has a narrow path in 
the centre, which admits of the internal operations being carried 
on with more facility. We have only seen this pit in use by 
the inventor, and, so far as we know, it is quite original. Mr. 
Saunders informs us that it answers the purposes of early forc- 
ing better than any other construction he has tried, and works 
admirably, in the severest weather, without the aid of fire. We 
have the fact of its perfect adaptability fully verified by its pro- 
ductions, and are so fully satisfied with its superiority as a 
dung-pit, that we are about erecting one ourself. It ought to be 
borne in mind, regarding this pit, that unless there be abundant 
supplies of fermenting manure always at hand when required, 
it would be useless to attempt forcing with it in winter ; but this 
fact also applies to all forcing pits heated solely by fermenting 
materials. 

Fig. 9 is the end section of a curvilinear-roofed cold-pit, for 
protecting plants not sufficiently hardy to stand the winter with- 
out protection, yet hardy enough to endure a considerable degree 
of cold, and even a slight frost, if kept in a dry state. Of this 
class we might name verbenas, roses, pansies, &c. Indeed, 
there are many summer flowers, used by the amateur, for the 
decoration of his parterre and flower-garden, which he might 
save, during the winter, in such a pit. The pit here given we 
consider the best, for any purpose to which the cold-pit can 
be applied. We have found them practically superior to all 
other pits we have yet used ; and as iron is now coming into 
general use, for the construction of horticultural buildings, we 
believe that these pits will be found, not only the most convenient, 
but also the cheapest that can be erected. #, shows the bed in 
which the plants are placed — we generally put in about a foot 
deep of tan, or saw-dust, for plunging the pots in ; — b, b, shows 
the sashes, elevated for the admission of air, supported by iron 
rods, c, c, which are made to enter a staple, by being bent, or 
hooked, at the end. 



46 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



Fig. 9. 




Fig. 10. 




STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 47 

Fig. 10 is a representation of an ordinary dung-bed, with the 
frame set on it. The formation of dung-beds is so simple as 
hardly to need a single word of explanation ; nevertheless, a 
few passing remarks may be useful to the uninitiated. 

Hot-beds of fermenting materials are generally laid on the 
surface of the ground. Some prefer the basis of the bed to in- 
cline slightly towards the horizon ; but we can see no utility 
whatever in this system, except the site of the bed be very wet, 
and then we prefer building the bed on a layer of brushwood. 
It is also beneficial to place a layer of brushwood every eight or 
ten inches deep, which lets the rank heat and steam escape 
more readily. The bed should have a slight inclination towards 
the south, when the frame is laid, though this rather tends to 
prevent the bed heating equally all over; and, where light is 
not an object, as in cutting-beds, &c, we prefer it quite level, 
and even inclining towards the north, the inclination of the 
frame turned in the same direction. 

Temporary or portable frames* or cases, for covering beds, 
and protecting plants, are exceedingly useful about places where 
it is requisite to harden young plants, or protect individual 
specimens in the open ground. 

Fig. 11 shows a portable glass frame, of a rectangular shape, 
and which we have often found useful for hardening young 
stock, in the early part of summer, which was intended for bed- 
ding out in the flower-garden. It can also be set on a dung- 
bed for growing early melons, cucumbers, and starting young 
plants into growth ; for this it is admirably adapted, as the light 
is admissible all round. 

A portable frame of this kind may be made of any size. We 
find, however, that about four feet wide, and six or eight feet 
long, is the most convenient size for practical purposes. 

Fig. 12, the portable plant protector, which will be found 
exceedingly useful for covering individual plants, standing in 
the open ground. Those may be glazed with coarse glass, or 
covered with oil-cloth. They will be found of much utility in 
covering the more tender conefirs during winter, as well as dur- 
ing summer from the intense heat. By having the south side of 
the case painted with a slight coat of a lime solution, to darken 
5 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



Fig. 11. 




Fig. 8. 



Fig. 12. 





STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 49 

the glass and prevent the entrance of the solar rays in that 
direction, the plants are better able to endure the extremes of 
either heat or cold, than if exposed or covered with straw or 
mats. 

In using these protectors for winter covering, it is only neces- 
sary to throw a garden mat over the case during severe frosts, 
removing it when the weather becomes mild, or immediately on 
the relaxation of the frost. There is not the slightest injury 
resulting from the taking off the mats, as would be the case with 
mat and straw coverings without the protector, as a body of air 
is always at rest inside, which prevents the temperature from 
falling so low as to cause injury to the tree. 

Framing-Ground. — This term seems to have a very different 
meaning in American gardens from what it has in England, for 
we find the spot usually appropriated to the pits, frames, hot- 
beds, &c, located in some out-of-the-way corner, with dung, 
weeds, and rubbish lying about in all directions, or, perhaps, we 
may observe them occupying a place in one of the squares of 
the garden, a site equally objectionable. 

Where frames and hot-beds are extensively used, they should, 
by all means, have a place appropriated to themselves, and 
sheltered, if possible, on the east, north, and west ; and, as we 
can see no reason why this department of the garden should not 
be visited by the proprietor as well as any other, it should be 
laid out and kept in a manner to make it worthy of a visit. In 
fact, the frame-ground should come as naturally in the course 
of promenade as the larger fruit houses. Every one, indeed, 
may not take the same interest in this department as in others 
of the garden, but this can form no excuse for huddling the 
frames and hot-beds into some recess, out of the way, and pay- 
ing no attention to order and cleanliness about them. Who, 
that is in the habit of frequently visiting large gardens, has 
not heard the gardener apologizing for the filthy condition of 
his frame-ground, when the curiosity or interest of the visitor 
led him thither ? The only reason that can be given for this 
state of things is, that the frame-ground is seldom intended to 
form a prominent object in the establishment ; its object being 



50 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

altogether for utility, it is considered by many a matter of 
absurdity to make it also an object of beauty. 

If gardeners would consider how much gratification they 
sometimes lose themselves, by depriving this department of the 
garden of its interest by proscription, they would exert them- 
selves more to bring it forward into its right place. If it is not 
a source of interest to others, it should be made so to the pro- 
prietor, for it must not be forgotten, that the pleasure and satis- 
faction derived even from culinary hot-beds and forcing-pits, 
does not wholly consist in their receiving the produce thereof, 
when ready for use, — for if so, recourse need only be had to 
the markets, — but, also, in marking the progress of their devel- 
opment, from the commencement to the close of their growth, 
in beholding fruits and vegetables flourishing in an artificial 
climate, and in the satisfaction of partaking of products of our 
own growth. 

When the ground rises towards the north part of the garden, 
this is doubtless the most eligible site ; although we are aware 
that some prefer placing them within an enclosure inside the 
garden, yet we think they are better placed near the northern 
boundary. As dung is at all times necessary, and at all times 
being carted to the frame yard, it is a continual nuisance having 
it taken over clean gravel walks. It is, above all things, desira- 
ble to have the spot approachable by carts, without in any way 
coming upon the gravel walks, which are appropriated only to 
promenade. 

Fig. 13 shows the disposition of the forcing-houses, frames, 
etc., at a gentleman's residence in the country, which is now 
being executed under our direction. The ground on the north 
side of the garden rises somewhat abruptly from the principal 
range, which gives the houses a fine aspect and a dry site. 
Immediately behind them, and stretching along the whole length 
of the forcing-pits, and frame-ground, compost-ground, etc., is a 
belt of trees, which have been planted expressly for the purpose 
of sheltering the spot from the north and north-eastern winds, 
the same object being attained by rising ground and plantation 
on the west. Abundant space is left between the different 
erections to afford room to promenade and inspect the whole 



r 



r 

















i \ 

M 

J : 
: 5 


«s 




^ 


LJ 












! 3 



-J 



5*= 



52 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

department, without being annoyed with manure under foot. 
Here, also, sheds and offices have been erected for the various 
purposes of the establishment, and arranged with a due regard 
to convenience and economization of labor in the operations 
daily going on in this department of the garden. 

The position of the framing-ground should command a good 
supply of water; either a natural stream should be brought 
through it, or a plentiful supply kept in a large tank, as in the 
plan, Fig. 13, and kept always full for immediate use, either by 
means of a water-ram, or other forcing-power. Pipes should be 
led from this large tank or reservoir into small tanks, one of 
which should be in each house, to be kept at the same tempera- 
ture of the atmosphere of the house in winter, for watering the 
plants. These tanks should receive the water from the roof, 
and be supplied from the reservoir, when that is exhausted. 

Fig. 13 is a ground plan and arrangement of frame-ground 
designed by the author for a gentleman's garden. 



REFERENCE TO PLAN. 

a Orange house. 
b b Vineries. 
c c Vine-stoves for forcing in winter, the vines being grown 

in pots. 
d d Culinary stoves. 
e Cold frames. 
/ Water tank. 
g Open shed for soils. 
h Seed room. 
i Garden office. 
j Miscellaneous store room. 
k Potting room. 
I Store room for pots. 
m Tool house. 
n n Large beds, in which green-house plants are plunged in 
ashes during summer, being covered, during the 
heat of the day, with awnings fixed on rollers, 
mounted on a slight frame-work. 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 53 






3 






54 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

2. Graperies, Orangeries, fyc. — These we have distin- 
guished from forcing-houses, as not being stimulated before their 
natural season of growth, artificial heat being sometimes applied, 
however, for their protection from early frosts in spring, and for 
ripening the fruits or accelerating the maturation of the current 
year's shoots in autumn. 

A greater latitude may be taken, in the construction of houses 
of this class, both as regards extent and ornament. Here the 
taste and wealth of the proprietor may be indulged to any 
degree. These structures may vary in length from 30 to 100 
feet, or more, although we prefer them to be limited to the lat- 
ter dimensions, adding others of different proportions, rather 
than continue the unbroken flatness of the roof beyond this 
extent. 

Fig. 14 represents a range of houses of this class, erected by 
John Hopkins, Esq., in the gardens of his splendid country-seat 
at Clifton Park. This is one of the most extensive structures 
of this kind yet erected in this country. It is three hundred 
feet in length, by twenty-four in breadth. The structure is 
divided into three compartments of one hundred feet each ; the 
centre compartment, which is larger and loftier than the others, 
is appropriated to the growth of orange trees planted in the 
ground, which, in a few years, will form a complete orchard of 
orange and lemon trees. 

The site of these houses is one for which nature has done com- 
paratively little, but for which art and outlay have done much, 
and for which the taste and munificence of the proprietor are still 
doing more ; but, like many other structures which have come 
under our observation, they contain much inferior glass in the 
roof-sashes, which is very injurious to tender foliage. Bad glass 
is an abundant material in the United States, and is generally 
used by tradesmen, who do the work by contract, on account of 
its cheapness. This is a matter which demands particular 
attention from those erecting horticultural buildings ; otherwise, 
they may not discover the error, until too late to prevent it. 

Fig. 15 is a representation of a model house for growing 
grapes on the lean-to or single-roofed system; and, both in 
regard to its dimensions and slope of roof, is just such a struc- 






STRUCTURES ADAPTED TO PARTICULAR PURPOSES, 55 



r 



B 



I 




56 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

ture as we would recommend — that is, if a lean-to house was 
desired by the erector, or the position would not admit of any- 
other kind. We need hardly mention that houses of this kind 
are suitable in many positions where curvilinear houses would 
be inappropriate, and where span-roofed houses would be 
impracticable. This house is at once cheap and substantial, 
in every way adapted for grape-growing, and presenting as 
good an appearance to the spectator as one that would cost 
double the sum, without any corresponding advantage. 

Fig. 16 is a span-roofed house on the same scale and the 
same design. Of course, span-loofed houses are to be preferred, 
either for plant-houses or for cold vineries, to lean-to houses, 
although, as we have said, there are positions which render 
lean-to houses preferable, even as cold houses. Span-roofed 
houses cost somewhat more in their erection than single roofs ; 
nevertheless, we consider it a matter of economy to erect a 
span-roofed house where the position is suitable, because the 
difference of cost is not so much as the difference of glass sur- 
face available for the growth of vines. In fact, a span-roofed 
house gives just two single-roofed houses of the dimensions of 
one of its sides. Hence, it is clear, that as many grapes can be 
grown in a span-roofed house, 50 feet long and 20 feet wide, as 
in a single-roofed house, 100 feet long and 10 feet wide, while 
the back wall, 100 feet in length, is saved. 

From the principles we have laid down for the construction 
of hot-houses, in the beginning of this section, it will be apparent 
that double-roofed houses are in every way superior to single 
ones for the general purposes of horticulture, not only on account 
of their superior lightness, but also as regards cost of erection. 
And we find this fact is now becoming generally admitted, from 
the prevailing tendency to erect double-houses, all over the 
country, where the advantages of double roofs are not sacrificed 
to the desire of having a more imposing and extensive appear- 
ance from a single point of view. 

Amongst the various forms of curvilinear houses lately brought 
under our notice, is that of forming the roof of the segment of a 
circle, which shall equal the width of the house, — a principle 
which we think is not generally recognized, nor do we think it 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



57 




[ 





58 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

applicable except under certain circumstances. We have seen 
houses erected on this principle in Northern Europe, where they 
doubtless answer the purpose much better than houses with ellip- 
tical roofs, for the reasons already stated in regard to forcing- 
houses; viz., the deficiency of perpendicular light, not only in the 
winter and spring, but also in the early part of summer, when all 
the perpendicular power of the sun's rays is required for the proper 
maturation of the fruit. It must be evident, however, that these 
reasons can be of no influence on this side the Atlantic, at least, 
in the southern and midland states, although we know of several 
houses in the state of New York, built on this principle, or a 
very near approximation to it. 

Fig. 17 is a single-roofed curvilinear house, built on the above 
principle, the back wall being equal to the breadth of the house. 
As a single-roofed house, this curve has a very good appearance, 
and answers admirably where perpendicular light is desirable. 
The only objection that can be urged against it, is the flatness 
in the upper portion of the roof, which gives it the same faulty 
character, for our hot climate, that we have urged against the 
flat roofs of straight-lined houses. 

Fig. 18 is intended to represent a double-roofed house, on the 
same principle. Here the width of the house must be equal to 
the chord of both the sides. The parapet wall being only a con- 
tinuation of the semi-circle, of course this form of house is open 
to the same objections as the other, (Fig. 17,) even in a greater 
degree, as the flat part of the roof, in this case, is precisely 
doubled. The perpendicularity of the rays is in some measure 
obstructed by a portion of the segment, at the apex of the roof, 
being opaque, as in the case of the house from which our sketch 
is taken. This plan answers the purpose very well, without 
depriving the house of its effect, and we think, where it is neces- 
sary, the effect might be heightened by a slight balustrade, or 
other ornament. 

That curvilinear houses, properly constructed, are superior to 
those with plain roofs, can hardly be questioned on practical or 
scientific grounds. The construction of the monster palm house, 
lately erected in Kew Gardens, at London, is an evidence that 
this principle is recognized by the most scientific cultivators in 






STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 59 

that kingdom ; and though the immense structure is avowedly 
for the growth of palmaceous plants, still the objections that 
might be urged against its modification as a palm-house might, 
with equal propriety, be urged against its form as a fruit house, 
on a smaller scale. If there be any fault in its curvilinear con- 
struction, the fault is augmented as the dimensions of the 
structure are increased. 

The objections that have been urged against curvilinear 
houses in England can have little application in this country, 
whatever force they might have in the cloudy climate of North- 
ern Europe. And we cannot help thinking that the arguments 
against them have, in a great degree, promoted their adoption, 
on account of the inconsiderate manner in which their mode of 
structure has been questioned. We think it clear, that any form 
of curvilinear roof, from the common rectangle to the semi- 
ellipse, or the acuminated semi-dome, not only admits of a larger 
run of roof, but also a larger proportion of light, than any form 
of straight-lined roof that can be adopted, excepting the polypro- 
sopic roof, which, in fact, is nothing more than an approximation 
to the curvilinear, or spherical roof, having the advantages of 
the one, without the disadvantages of the other. 

Another remarkable property possessed by curvilinear roofs, 
and not by straight-lined ones, is their power of reflection and 
refraction, which, in the hot summers of our climate, is of much 
more importance, in a horticultural point of view, than is gener- 
ally supposed. Though the power of curved surfaces of reflect- 
ing the rays of light be similar to that of plane surfaces, yet the 
plane is so small on which the rays fall, that its position is changed 
before its concentration can cause injury to the foliage on which 
it falls. As the surfaces of curvilinear roofs are, or ought to be, 
presented more obliquely to the sun's rays than straight-lined 
roofs, the amount of refraction, in very hot weather, will be 
greater in the former than in the latter case. The more ob- 
liquely the ray falls on the medium of refraction, the greater the 
amount refracted. 

The general form of curvilinear-roofed houses, in this country, 
is the common curvature already described, forming the segment 
of an ellipse, the ends being upright as in straight-lined houses. 
6 



60 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

For the purposes of grape-growing, we think a loss of surface is 
sustained by the position of the gable ends. In fact, from a series 
of calculations, bearing directly on this question, we have found 
in some houses that stand apart from other structures a loss 
equal to one third the extent of the roof surface. Some houses 
may be less, bat some more, than this amount. In growing 
grape-vines for instance, we know that the rafters — or the slop- 
ing part of the house — is the principal area for the fruit-bearing 
branches of the plant. Now, supposing that your house be 50 
feet in length, 15 feet wide, and as many feet high, then, by 
having no vines of any account growing on the ends of the 
house, you lose a transparent surface equal to nearly one half 
the extent of the whole roof. If it be asserted that the perpen- 
dicularity of the gables is necessary for the admission of hori- 
zontal light, we think this wholly unwarranted ; for experience 
has fully proved that horizontal light, entering by the medium 
of upright glass, is powerless, comparatively speaking, for assim- 
ilating the juices, either in proper quantity or quality, for the 
production and maturation of fine fruit. Many of the oldest and 
most experienced gardeners prefer hot-houses having no upright 
glass at all in front, placing the roof directly upon a parapet 18 
or 20 inches in height. 

By way of remedying the objection here pointed out, we have 
designed a house which combines the advantages of a curved 
roof with those of a plane surface, rendering the whole of the 
house available for the production of fruit. By this plan a 
greater training surface is obtained, for the same extent of glass 
surface, than by any other we know, or in any other structure 
of similar dimensions. This we consider the most perfect form 
of a hot-house that has yet been erected. 

Fig. 19 is intended to convey a clearer notion of the kind of 
house we have referred to. This house is 100 feet in length, 
20 feet in height at the back wall, with a perpendicular rise of 
five feet. The roof rises in series of successive planes, from the 
upright front, and presents a continuous surface for training the 
vines to, from one end to the other. Fig. 20 shows the ground 
plan of the house, which may be made of any dimensions, as 
easily as any of the common forms. 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



61 




3 







LZi 




r~ 







62 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

A double-roofed house can be erected on the same plan, by 
substituting a row of columns along the centre of the house for 
the support of the ridge, in place of the back wall; one of the 
planes being raised the necessary height at each end, for the 
doors, which must also be done in the single roof, (Fig. 19,) 
unless the door enters through the back wall, which, in some 
cases, may not be so convenient as having them at the ends, 
though, for the economizing of glass surface, we would prefer 
them in the back wall. 

Although double-roofed houses are generally of a rectangular 
shape, yet they admit of every combination of form without 
militating against the admission of light and air. Nevertheless, 
that they may be perfectly adapted to the end in view, there are 
rules to be observed, and errors to be guarded against, which it 
is necessary here to point out. 

If the house is above fifteen feet in width, it is necessary to 
have a single or double row of columns in the centre to support 
the ridge of the roof, but in many houses these columns are 
three times thicker and heavier than they ought to be, even with 
a due regard to strength and durability. When the columns 
are disproportionately heavy, the house has a dull and clumsy 
appearance, and the effect within is extremely bad. Indeed, 
columns ought to be dispensed with where they can possibly be 
spared, consistent with strength in the structure. We have 
frequently seen the internal view of double-roofed houses com- 
pletely spoiled by the clumsiness of the columns supporting the 
roof, even when columns were altogether unnecessary. Cast- 
iron columns are always preferable to timber, even when the 
structure is made of the latter material. When the columns or 
rafters are bound together by braces and crossbars of slight con- 
struction, as of iron in different forms, vines and other climbing 
plants may be trained upon them, and be hung in festoons from 
column to column, or otherwise, as fancy may dictate; this 
gives an elegant appearance, and is always pleasing to the spec- 
tator. 

Another common error in the construction of fruit-houses is, 
the heaviness and height of the front, something in the fashion 
of the heavy and dull-looking plant-houses of the last century. 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 63 

This results from a very general desire to give the structure a 
finer effect from a front view; but it must be regarded as a 
decided sacrifice of utility and adaptation to purpose. Making 
the front of graperies from eight to ten or twelve feet high, 
is not less objectionable than to make the roof on a level with 
the plane of the horizon. The sides of a hot-house should never 
be more than four or five feet in height. This gives the struc- 
ture a more characteristic appearance, and is certainly much 
more fitted for the purpose in view, than upright sashes, which 
make the roof appear to the eye only a fraction of its real extent, 
whether viewed from the interior or the exterior of the structure, 
apart from the consideration, that the upright part of the house 
neither produces nor ripens the berries of grapes so well as the 
sloping part of the transparent surface. All structures of glass, 
for horticultural purposes, should have a parapet wall, from 12 
to 20 inches in height, on which to rest the frame-work of the 
fabric ; then about four feet of upright glass. This modification 
gives the house, whether of large or small dimensions, a neat 
and characteristic appearance. A span-roofed house, 24 feet 
wide and 16 feet high, with a five-feet front, makes a well- 
proportioned house, and gives about 16 feet of a run for the 
vines under the rafters, — the slope of the roof being upon an 
angle of 45°, which, as we have already said, is the best pitch 
for a hot-house roof for general purposes. 

Until these few years, the forms of hot-houses were generally 
plain, flat, right-lined buildings, differing in no respect from one 
another than in their size and relative degrees of clumsiness. 
Lately, however, a great improvement has taken place in the 
form and construction of this class of buildings. Single-roofed 
houses are fast dwindling into desuetude, and right-lined houses 
are giving way to the more light and elegant curvilinear roofs. 
This is an important step in the right way; and we regard 
those who, laying aside their prejudices in favor of right-lined 
houses, adopt the curvilinear shape, as conferring a benefit on 
exotic horticulture as acceptable to those interested in the pro- 
fession as it is creditable to themselves. 

Regarding curved houses, Loudon says, — " On making a 
few trials, to ascertain the variety of forms which mio-ht be 
6* 



64 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

given to hot-houses by taking different segments of a sphere, 
I, however, soon became fully satisfied that forcing-houses, of 
excellent forms for almost every purpose, and of any convenient 
extent, might be constructed without deviating from the spheri- 
cal form ; and I am now perfectly confident that such houses 
will be erected and kept in repairs at less expense, will possess 
the important advantage of admitting much more light, and will 
be found much more durable, than such as are constructed 
according to the methods and forms which have hitherto been 
recommended." 

Fig. 21 is a representation of what is called the zig-zag, or 
ridge-and-furrow roof, which has not, as far as we know, been 
very extensively adopted. There are several places in Eng- 
land where this method of roofing has been adopted, but prin- 
cipally as an experiment, or merely as the fancy of the erector. 
The advantage of this mode of roofing is, that the rays of the 
sun are presented more perpendicularly to the glass in the 
morning and afternoon, when they are weakest, and more 
obliquely to the glass at noon, when they are strongest. We 
doubt, however, — though the arguments we have heard urged 
in favor of this kind of houses be indisputable, — whether the 
additional expense required in their construction will be coun- 
terbalanced by the advantages gained. There is no doubt the 
expense of their erection militates very much against them ; and, 
if they could be erected as cheap as plane roofs, they are decid- 
edly superior to them for graperies, as the vine can be trained 
up the middle of the ridge, and, consequently, though suffi- 
ciently near the glass, the intense rays of the sun will be less 
injurious than under a plane roof. 

The ridge-and-furrow roof may be carried out either on com- 
mon plane-roofed houses, or on the curvilinear principle, though 
doubtless the latter is more difficult of construction, and, of 
course, more expensive ; but we have no doubt, if the principle 
of constructing horticultural structures were fully understood by 
competent manufacturers, who had directed their attention to 
the details of the structures, that this, or, in fact, any other 
form of structure, could be made as cheap as the houses now in 
common use. 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 65 



Fig. 21, 




68 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

The ridge-and-furrow roof may be formed by placing the 
rafters as in making a common roof, say four feet apart; then 
placing the ridge-bars in such a manner that, contiguous to each 
other, they will form an angle of 45° with the furrow-bar, or 
rafter. Or the angle included within the ridge-bar may be 
formed to suit the climate of the neighborhood, — bearing in 
mind the principles already laid down regarding the effects of 
intense sunshine upon flat roofs. 

The sides of the ridge may be glazed of small panes, as in 
common sashes, or may be made of single panes, as in the finest 
houses now erected ; but, whichever method is adopted, the 
rafters should terminate in one horizontal line on the top of the 
parapet : this is also desirable at the back wall. Some apparent 
difficulty is thus occasioned in the lower part of the roof; but 
this difficulty is only apparent, especially if the front of the 
ridge be made to slope on the same angle as the side. Only 
the smaller and triangular pieces of glass can be used. It 
becomes, in fact, more economical, as the smaller pieces of glass 
may be all used up, which would, otherwise, be thrown away. 

The ridge-and-furrow roofs are especially advantageous in 
countries liable to heavy falls of snow or rain, and in large 
houses which are parallelograms in plan. Almost any weight 
of snow may be carried by such roofs, especially where the fur- 
row is small, as the pressure will then be chiefly on the bars 
and rafters, and not on the glass. As to hail, which is some- 
times very heavy in this country, breaking the glass in flat-roofed 
houses, it will always meet the glass of a ridge-and-furrow house 
at an angle which will prevent breakage. 

The advantages of these ridge-and-furrow roofs, as we have 
already stated, — their presenting the surface of the glass at an 
oblique angle to the noon-day sun, while the morning and even- 
ing sun is admitted almost perpendicular to the surface on 
which it falls, — ought not to be altogether overlooked in this 
country ; and we think that a great deal might be done with 
houses of this kind, — probably upon an improved plan, — where- 
by the effect of the intense sunshine of mid-summer might be, in 
some measure, deprived of its meridian force upon glass-houses. 
Whatever may be thought of the plan here given, the principle 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 67 

upon which it is made is undoubtedly good ; — a principle which 
may easily be illustrated by placing a few common frame- 
sashes in the positions of the supposed ridge-and-furrow roof, 
placing some tender-foliaged plants beneath them, and then 
comparing the results, under intense sunshine, with the effects 
produced under a common sash, whose surface is perpendicular 
to the noon-day sun. 

Whatever might be said in favor of cold vineries, they are, 
nevertheless, subject to casualties which are necessarily una- 
voidable. This is more especially the case in the Northern 
States ; and even as far south as the latitude from which we 
now write, (39° 45',) they are liable to the same mishaps. All 
houses for the production of foreign grapes should have some 
means or other of commanding a little artificial heat when it is 
found absolutely necessary. This does not amount to saying 
that good crops have not and may not be grown in cold-houses, 
without any means of raising the temperature in cold nights ; 
yet it cannot be denied that good crops have been sacrificed for 
the want of a slight fire in frosty nights. This is particularly 
the case in nectarine and peach houses, where we have seen the 
crop completely destroyed in a single night. 

Experience has fully shown that the culture of exotic fruits is 
a precarious business, without some readily available means of 
averting those evils which are neither modified nor averted by 
any peculiar mode of construction, or any angle that can be 
given to the roof. This circumstance is worthy of particular 
attention, as many persons who design hot-houses lay particular 
stress on certain trifling details in the structure, which, in a 
practical point of view, are unworthy of the least notice. 

We have lately had some conversations with men thoroughly 
skilled in the science, as well as the practice, of vine-growing 
and the details of hot-house management, and have particularly 
noted the diversity of opinion regarding the upright portion of 
the front of the house. Some are of opinion that hot-houses for 
the culture of fruit should have no parapet-wall, but that the 
sashes should rest on a water-plate level, or nearly level, with 
the ground, giving, as a reason, the fact that the parapet pre- 
vents the sun and light from getting to the inside border, and to 



88 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

the stems of vines. Now, with regard to small winter forcing- 
houses, this may be of some effect ; but in cold summer-houses, 
i. e., houses intended for growing peaches, grapes, etc., without 
fire heat, this is of no importance, as the meridian altitude of 
the sun during summer renders the wall rather beneficial than 
injurious, by shading the border during the heat of the day. 
Hence, it is evident that the construction of the house for 
grape-growing, etc., should be regulated according to the locality, 
as well as the period of the year at which it is required to ripen 
the fruit. 

Many have a serious objection to upright fronts, whether of 
glass or other material, from the undeniable fact that fruit is 
seldom produced below the angle of the rafter ; and if it is, it 
never ripens so well as that grown under the perpendicular 
light, nor is so well-flavored. Upright glass, however, adds so 
much to the appearance of this kind of building, that it can 
hardly be dispensed with, even at the sacrifice of a little fruit ; 
but the latitude here allowed must be kept within certain limits, 
otherwise the effect produced is worse than if the house had no 
parapet at all. 

The parapet wall of a peach-house or grapery should never. 
be more than twenty inches or two feet high; the perpendicular 
sash above it, three feet more, making the upright front five feet 
in all. This is, we think, a proper height for structures of the 
kind here referred to ; and this will be found to give the struc- 
ture, whatever its longitudinal dimensions, better proportions, 
and a more handsome appearance, than if these dimensions be 
either diminished or increased. 

In many private establishments it is much more convenient 
to have one, two, or more houses, than to have one single 
house perhaps equal to the length of the whole. We happen 
to know several persons who prefer erecting houses for grapes 
and peaches in this way ; and, indeed, it has many advantages 
over building a large house, especially for private establish- 
ments of moderate extent, where the whole produce is consumed 
by the family, because one house may be advanced a month or 
two before the succeeding one, while the third may be protracted 
as late as possible, so that the fruit season will be much longei 



STRUCTUKES ADAPTED TO PARTICULAR PURPOSES. 



69 



±± 



"IEEE 



H 



m 



70 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

than if the structure was composed of a single house of the size 
of the three. 

In building a range of hot-houses on these principles, say one 
hundred feet long, we would arrange them in the order rep- 
resented in the opposite cut, Fig. 22, showing three houses 
united into a neat and compact range. The centre division, 
which is more elevated than the others, may be used as an 
orangery, or camellia house ; or for growing figs, planting the 
trees in the centre bed and growing them as common dwarfs, 
which is the best way of growing figs, their strong and uncom- 
pliable branches being unsuited for training on the common 
trellises of a vinery, neither do they fruit so well as when 
allowed to grow like a dwarf pear-tree. 

These dimensions are also advantageous on account of the 
trees that are to be grown in them, as different kinds of trees 
require different kinds of treatment, as well as different degrees 
of heat, air, and moisture. Each kind of tree can have the 
treatment which is most conducive to health and fruitfulness, 
without infringing on the peculiar conditions required by the 
others. 

Where a large quantity of fruit is required, the houses for its 
production must, of course, be upon a larger scale. We men- 
tion this, as very absurd ideas are frequently entertained by 
individuals regarding the producing capacity of vines, etc., in 
houses, being ignorant of the quantity that healthy trees can 
bear without inflicting a permanent injury. 

If it be desired, the centre compartment of this range may be 
converted into a green-house, by placing a stage along the mid- 
dle of the house, and a front shelf two feet wide along the front 
nearly level with the building of the parapet wall, leaving a 
sufficient space between the shelf and the stage for a pathway. 
The plan of placing the green-house in the centre, between 
the fruit-houses, is very common. The plans of modern archi- 
tects are somewhat different from those of the last century, 
in which we generally find the green-house a part of the cul- 
inary department, either in the middle, or in a corner of the 
kitchen garden. In fact, little can be said in favor of placing 
the green-house or plant-stove among the fruit-houses, except 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 7] 

in small places where the limits of the ground do not admit of 
a select position, or where it may be desirable to place the whole 
of the glass structures together, either for economy, conven- 
ience, or effect. 

When a grapery having some pretensions to architectural 
display is desired, either to correspond with buildings already 
on the place, or to form a connection between some portion of 
the mansion and another, then the structure may possess a 
heavier and more artistic character. This may be accomplished 
without in the slightest degree infringing on the principle of 
adaptability. For instance, there may be a recess, with the 
proper aspect, in some part of the mansion, which the proprietor 
may wish to fill up with a house productive of profit as well as 
pleasure ; and for this purpose, he chooses a grapery, and wishes 
a suitable house for the purpose, without destroying the general 
harmony of his mansion. Or, perhaps, his premises may be 
very limited in extent, and he wishes a fruit-house nearly of 
the same order as his Tuscan or Italian villa ; in which case, a 
house with a somewhat massive parapet and blocking-course, as 
in Fig. 23, would be more in unison with his taste, as well as 
with the rest of the premises. 

This house, it will be observed, has rectangular ventilators in 
the front wall, which give the house a more architectural 
appearance ; the back wall is also surmounted by an ornamental 
blocking-course, with ventilators for the admission of air through 
the back wall. [See Ventilation.'] 

We do not, by any means, justify the method of placing 
fruit-houses immediately contiguous to the dwelling, yet such 
is the taste of many. And as there is no valid reason w r hy 
persons may not carry out their particular fancies with their own 
property, we have made the foregoing remarks for their benefit. 

We do not give the above cut as a model house for an archi- 
tectural vinery, — of course, its ornamental character may be 
increased, according to the money that is to be devoted to its 
erection ; but with regard to the principles of its design, unless 
the polyprosopic roof be adopted, which is considered by some 
more architectural in its appearance than curvilinear roofs, 
when conjoined to the square forms of dwelling-houses. 
7 



72 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 




STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 73 

3. Green-houses , Conservatories, fyc. — The principal dis- 
tinction between a green-house and conservatory is, that in the 
former, the plants are exhibited upon shelves and stages, while, 
in the latter, the plants are generally planted out in a bed in the 
middle of the house prepared for their reception. In many 
instances, however, there is no other distinction than in the 
name ; as these structures are sometimes so arranged that the 
middle portion is appropriated to the growth of larger plants 
planted out, while the sides are surrounded with shelves for the 
reception of plants in pots, as in a common green-house. And 
to this arrangement there can be no special objection, especially 
where the structure is of small dimensions, which admits of the 
sides being shelved for plants in pots, without destroying the 
character of the house, or the plants, by their distance from the 
glass. We have seen a few instances, a very few, where the 
two characters w T ere amalgamated together, forming a most 
interesting conjunction; but, unless the specimens exhibited be 
very large and well-grown, their effect, when situated upon the 
centre bed of a common-sized house, surrounded with shelves, 
is meagre and defective in the last degree. 

Properly speaking, a green-house is not a receptacle for large 
plants, and hence it should have adequate means within it for 
standing the plants within a proper distance from the glass. 
This is absolutely necessary with regard to those classes of flow- 
ering plants that are fitted to adorn it, both in winter and sum- 
mer. Some are of opinion that green-houses are of no further 
service than merely to store away a miscellaneous assortment 
of rubbish during the months of winter, for the obvious purpose 
of preserving them until the next summer, that they may turn 
them out under trees, or in out-of-the-way corners, to keep them 
from being burnt up by the hot summer sun ; and, as a matter 
of course and of custom, the green-house is converted into a 
lumber-room, or something else. And there it stands ! what is, 
or ought to be, the chief ornament of the garden, deprived of its 
character, for want of taste, and divested of its interest, for lack 
of skill! Visitors say, "Let us have a look at the green- 
house." " No," replies the gardener, apologetically, " it 's not 



74 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

worth your while going in, for there is nothing there to see ! " 
A humiliating acknowledgment, but full of truth. 

It is foreign to our purpose to enter upon the present condi- 
tion of green-house gardening, and the manner in which these 
structures are managed by gardeners. Our present object is to 
•treat of their construction, and of the means of adapting them 
the most easily to the culture of flowering plants, either during 
winter or summer. 

It is a well known fact, that plants that are grown in what 
are called lean-to green-houses, have exactly the character of 
the house in which they are grown, i. e., they are one-sided ; 
nor is it possible, without a vast amount of labor and attention 
on the part of the gardener, to grow them otherwise. In this 
respect the cultivator does not imitate nature, but rather the 
monstrosities of nature. Trees and shrubs only grow one-sided 
when their position precludes the access of light and air around 
them ; but they grow naturally into a compact bush, which is 
universally allowed to be the most beautiful form that plants 
can assume. 

Even a handful of cut flowers have their beauty, and are 
generally admired, but when seen upon the living plant, 
whatever shape or form the latter may possess, how much 
greater their charms ! If, therefore, we add to these natural 
beauties the additional charm of a positively beautiful form, 
surely it will double their claim to our admiration. And we 
may here add the gratifying fact, that this claim is now gener- 
ally recognized by all who can appreciate the superior beauty 
of w r ell-grown plants. 

The principles upon which plant structures ought to be built, 
are somewhat different from those which regulate the erection 
of forcing-houses, culinary houses, &c, and as their purposes 
are different, their shapes and forms are generally also different. 
Plant-houses admit of a greater variety of shape and design 
than any of the kinds previously mentioned, and as they are 
generally erected in private grounds, for ornament and display, 
they should have a more artistic character than the others. 

The size of the green-house may vary according to the extent 
of the collection to be cultivated, but it should always have a 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 75 

length proportionate to its height and width. There is a great 
inconvenience in having the green-house very capacious, and 
where it is desirable to have a large collection of plants, it is 
best to have a conservatory for the growth of the larger speci- 
mens, or a stove for the palmaceous families of plants. We 
shall, however, allude to what is properly termed the green- 
house. 

A first-rate green-house should be completely transparent on 
all sides ; lean-to houses are decidedly objectionable, for the 
reasons already given. Houses that are only glazed in front, 
and have glass roofs, but otherwise opaque, are also objection- 
able, as plants can never be made to grow handsome. They 
become weakly and distorted by continually stretching towards 
the light, neither do they enjoy the genial rays of the morning 
and evening sun, and only perhaps for a few hours during mid- 
day. If such houses be large and lofty, they are still more un- 
manageable, as no culture can keep the plants symmetrical and 
of good appearance. 

A green-house should stand quite detached from all other 
buildings, and may be of any form the fancy may dictate, or the 
position suggest. It may be circular, oval, hexagonal, octagonal, 
or a parallelogram, with circular or curved ends. The house, 
to be proportionate, should be about fifty feet in length by twenty 
in width, and fourteen feet high, above the level of its floor; if 
more effect be required from the external view, its parapets may 
be raised, to give the house a loftier appearance. The parapet 
should be not more than two feet high all round, the upright 
glass about two and a half or three feet more, including base, 
plate, and sash bars. The house should be surrounded by a 
shelf, two feet wide, level with the top of the parapet wall. 
This shelf is of great importance to a gardener, and is gener- 
ally the best place for the finer kinds of plants ; being sur- 
rounded on all sides with light, and being near the glass, they 
grow bushy and dwarf in habit, in which state they are most 
pleasing and attractive. Next to this shelf comes the pathway, 
three feet wide at least, (having just enough room between the 
roof for the tallest individual to clear the glass and rafters;) 
then the stage, or centre-tables, of stone or timber, and arranged 



76 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



according to the size of the plants to be grown. The following 
end section will illustrate what we here refer to. It is somewhat 
enlarged, for the purpose of showing the arrangements of the 
interior. The cut which follows (Fig. 25) is a perspective view 
of the same house, taken at a considerable distance from it, for 
the purpose of showing the effect of this plain structure in a 
pleasure-ground. If desired, it may be made to assume some- 
thing of the character of a conservatory, by introducing a ground 
bed in the centre, instead of the shelves or tables. The fire- 
place and heating apparatus may be placed at one end, and 
under ground, so as to be out of sight, or may be formed in a 
sunk shed, and blinded with shrubbery. The flues, or pipes, for 
warming the house, must be carried round, beneath the side 
shelves, dipping below the level of the floor at the doors, and 
returning by the opposite side of the house to the furnace. The 
cost of such a structure will very much depend upon the quality 
of the workmanship, and the material used in the construction ; 
but we think a very good house may be erected, according to the 
foregoing plan, for about ten dollars per foot in length, or about 
five hundred dollars for a house 50 feet long by 20 feet in width. 

Fig. 24. 




Such a green-house, though plain and inexpensive in its 
character, may, nevertheless, be made to harmonize well with 
flower-garden scenery, and is far superior to the clumsy, shed- 
like erections frequently seen stuck into corners of buildings 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 



77 



and dwelling-houses, without reference to the position of the 
structure, or the purpose for which it was built. 

Fig. 25 shows the appearance of the house, on the proportions 
which are given in the above plan, (Fig. 24,) which, in our 
opinion, admits of more room for plants than any other form 
that can be built at the same cost ; for, although we might adopt 
a semi-circular form for the end toward the most prominent 
point of view, it must be remembered that this would add con- 
siderably to its cost. Our object here is to give the sketch of 
the best and cheapest kind of house that can be erected for plant- 
growing, and such is the one here given. 

This house may be placed in any situation, as regards aspect. 
It may be attached at one end to any other building, without 
much injury to its efficiency as a plant-house ; and where it is 
found absolutely necessary to attach green-houses to the walls 
of other buildings, they should, by all means, be constructed 
after the plan here given, or under some architectural modifica- 
tion of it, avoiding, if possible, that old, and now almost obsolete, 

Fig. 25. 




system, of laying the roof up to the wall, as in a common 
grapery, or of making the front of heavy pilasters and massive 
wood-work, like the orange-houses of the middle ages. The 
method of construction here described is that in which the 
plants enjoy the largest share of light ; and this house is the 
easiest managed — with respect to air and heat in winter, and 
moisture and shade in summer — of all other methods which 
have come under our experience. 



73 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 






ran 



USD 




STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 79 

In some establishments it may be requisite to have a range 
of plant-houses, or one house divided into compartments, for 
the different kinds of plants ; thus the structure may be of a 
highly ornamental character, as in Fig. 26, one end consisting 
of a common green-house, for geraniums and soft-wooded plants, 
and the other may be either a heathery, an orchidaceous, or an 
exotic stove, for promiscuous plants ; the centre, being larger and 
more capacious than the ends, may be an orangery, or a palm- 
house. 

This forms an elegant range of botanic hot-houses, and being 
of glass all round, should stand in the middle of a large pleasure- 
ground, or shrubbery. The smoke of the furnaces, being con- 
ducted into a subterraneous canal, is carried to a distance, and 
emitted by means of a shaft having the appearance of an orna- 
mental column, as in the Botanic Gardens of Edinburgh and 
Kew. 

By having the plant-stove in the middle of the other houses, 
a considerable advantage is gained by the protection afforded in 
winter, when the structure requires to be kept at a high temper- 
ature by artificial means ; and as both of the adjoining houses 
will also be warmed in severe weather, the centre one, though 
larger, will be maintained at the required temperature with a 
heating apparatus no larger than the others. 

From the curved disposition of the centre house, this range 
has a peculiarly pleasing effect, when viewed from a horizontal 
point of view somewhat distant. The proportions of this struc- 
ture are excellent ; and it would, undoubtedly, form a splendid 
ornament in the grounds of a gentleman's country-seat. 

One of the leading errors in the erection of large plant-houses, 
is in the unreasonable height to which their roofs are carried, and 
which in the case of palm-houses maybe defended as necessary; 
but in the case of conservatories, there is no tenable justification 
of such a course, except the house is intended to be the object 
of admiration, instead of the plants that are grown in it ; and 
if fitness for the end in view be expressive of beauty, then, after 
all, these architectural temples must decidedly fail in producing 
that effect upon the mind, that the plain finished, but fitly and 
efficiently designed structure never fails to produce. But the 



80 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 




STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 81 

beauty, even of the plainest kind of structures, may be easily 
heightened and increased by an ornamental moulding of wood 
along the ridge of the roof, if a span, or on the end rafters and 
front plate, as in Figs. 26 and 27, which will deprive the house 
of none of its lightness, and will give it a neater and more ele- 
gant appearance. 

Plants placed at a distance, either under water or under glass, 
are as much influenced in their development by the light as by 
the heat. When plants are a great distance from the roof, they 
are, of course, in a colder and denser medium at the surface of 
the soil than at the top of the house, and there cannot be a 
doubt that this difference in the density and temperature of the 
atmosphere has much to do with the struggle and effort which 
every plant makes to rise upward, and to elevate its assimilating 
organs into the warmer and most humid regions of the house. 
It will also be found that the difference betwixt the higher and 
lower strata of air in hot-houses, is more immediately the cause 
of plants drawing, and becoming weak, than anything that re- 
sults from a feeble constitution, or from a deficiency of atmos- 
pheric air. 

Notwithstanding the practical illustrations of this prevailing 
error in plant-houses, there seems to have been very little done 
to counteract this fault in lofty houses. The large conservatory 
in the Regent's Park, Botanic Garden, is the only structure of 
great size where this circumstance has had sufficient weight to 
induce the erectors to provide against it, in the general design 
and construction of the building. This admirable plant-house 
stands as a striking illustration of what can be done on a grand 
scale, without rendering fitness for the end in view subservient. 
to architectural display, and yet, without depriving the structure 
of that dignity and effect which fine conservatories always convey 
to the cultivated mind. This conservatory, we believe, is the 
result of well digested practical and scientific knowledge, and 
we doubt if there be any other such erection in England, where 
the effect of this rare combination is so strikingly displayed on 
a scale so magnificent; and the result of this combination has 
indeed been clearly manifested, in the formation and subsequent 
management of this beautiful garden. 



82 STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

As the influence of the upper and lower strata of air, in large 
houses, will be discussed in a subsequent portion of this work, 
devoted to that subject, we will not enlarge further upon it at 
present, more than to observe, that lofty-domed, or curvilinear 
roofs, as that lately erected at Kew, are more difficult to manage, 
both in winter and summer, than low-roofed houses, whether 
curved or straight, and that the impossibility of rendering these 
houses in any way workable, has induced, in some instances, 
their almost entire abandonment on the part of the proprietors, 
owing solely to the intense heat of the superior regions of the 
house. 

The most experienced and enlightened men have satisfied 
themselves, that structures in which the atmosphere has to be 
kept at a higher temperature than the external atmosphere, and 
in which, plants have to be grown, should be kept at the very 
lowest elevation which the use and purpose will admit, so that 
the temperature of the air, at the level of the floor, and among 
the roots and lower portions of the plants, may be as little dif- 
ferent as possible from what it is in the higher regions of the 
house ; by regarding which, the house will be much easier kept 
during summer, with respect to air and moisture, arid, during 
winter, with respect to a more equal diffusion of heat. 

In the comparatively still atmosphere of a hot-house, when all 
is closely shut up in a cold winter's night, the difference betwixt 
the temperature of the atmosphere at the surface of the floor 
and the highest part of the roof will generally be in the ratio 
of one degree to every two feet of elevation ; thus, in a house 
20 feet high there will be a difference of 10°, and in a house 60 
feet high the same rule gives a difference of no less than 30 de- 
grees. This ratio, however, is not absolutely correct, as we 
have proved by experiment, in houses of various sizes, which 
give, under certain circumstances, a greater difference of tem- 
perature than here stated, as will be shown when we come to 
treat on this branch of horticultural science.^ 

We have already said enough on this point, here, to show the 
advantage of erecting low-roofed conservatories, especially when 

* See Ventilation. 



STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 83 

the object is to grow the plants in beds, or masses, irregularly 
placed on the level of the floor, which is decidedly an improve- 
ment upon the old method, of having a few long-legged and 
branchless specimens sticking their heads up to the glass, where 
their leaves and flowers are far above the common axis of vision, 
and where nothing is seen below but the monotonous bed, and 
the bare stems of the plants that are growing in it, compelling 
the gardener, at all hazard of propriety, and in violation of 
every principle of taste, as well as of his own judgment, to stick 
in the commonest plants, whatever they are, among the bare 
stems of the others, to fill up the unsightly blanks and vacancies 
thus occasioned in the beds. 

While on this subject, we will just briefly remark, that nothing 
has so much tended to improve the culture of the trees and 
shrubs, generally grown in houses of glass, as the improvement 
that has taken place in the mode of construction. AH practical 
men are agreed on the point, that, to grow plants well, the 
house must be low in the roof, and light as well as air must be 
admitted freely to every part of the plant, from the ground to 
the glass. They must also be situated in such a way, regarding 
their lower parts, that the light may not be obstructed, for how- 
ever powerful, and perhaps sometimes injurious, the fierce 
rays of the mid-day sun may be in mid-summer, yet its perma- 
nent obstruction is far more so. It is easier to obviate scorching 
in the one case, than etiolation in the other. 

8 



SECTION IV. 

INTERIOR ARRANGEMENTS. 

1. Arrangements for the interior of forcing-houses, culinary- 
houses, &c, are generally very much alike, consisting chiefly 
of trellises of wood, or of wire, to which the trees are trained. 
The other portions of interior detail are common to horticultural 
structures of every description, and w r ill be subsequently de- 
scribed in their respective places. 

" Half the advantages," says Loudon, (Ency. of Gard.,) " of 
culture, in forcing-houses, would be lost without the use of trel- 
lises. On these the branches are readily spread out to the sun, 
of whose influence every branch, and every twig, and every leaf, 
partake alike ; whereas, were they left to grow as standards, un- 
less the house were glass on all sides, only the extremities of 
the shoots would enjoy sufficient light. The advantages, in 
respect of air, water, pruning, and other parts of culture, are 
equally in favor of trellises, independently, altogether, of the 
influence which proper training has upon fruit-trees, as the vine, 
the peach, apricot, &c, to produce fruitfulness." 

Notwithstanding the obvious utility of trellises in culinary 
houses, the use of them is frequently carried to a most unprofit- 
able and injurious extent, when the whole interior of the house 
is filled with foliage from the glass to the floor. Here, work is 
entailed upon the gardener to no purpose ; and though good 
crops may be borne on the trees that are trained upon the trel- 
lises crossing the house, or on the back wall, the fruit is utterly 
worthless. 

The trellis, situated on the back wall, was formerly considered 
the principal part of the house, for producing a crop ; but this 
is only the case in small, narrow houses, and where no trees 
are trained upon the rafters, or under the glass. Experience 
has proved that, where the whole surface of the glass is covered 



INTERIOR ARRANGEMENTS. 



85 



with foliage, there is very little gained by training either peaches 
or vines on the back wall. 

The principal use to which back-wall trellises may be profita- 
bly turned, is for the cultivation of figs, which are found to do 
much better than peaches under the shade of others. 

The trellis, whatever its form, should be as near to the glass 
as possible, and placed so as to command the full influence of 
the light entering the house. When the vines are trained upon 
the single rafter trellis, Fig. 28, A, leaving the middle of the 
lights open, for the free admission of light to plants beneath, then 
the curvilinear trellis may be introduced into the centre of the 
house, as represented at a, Fig. 29, from which good peaches 
and nectarines may be obtained, providing the sashes be kept 
open in the middle, as already stated, for the admission of the 
unobstructed light. 

Fig. 28. 



A. 



B. 



The most common method of fixing the roof trellis is by studs, 
Fig. 28, B, screwed into the rafter, about eight inches distant. 
Each stud is provided with an eye, or hole, at the extremity, 
through which the wire is passed, and tightened at both ends 
by screws and nuts. The studs should not be less than twelve 
inches in length, so as to afford room for the foliage to expand 
itself fully, without coming in contact with the glass, which, 
when moistened with the condensed vapor, is apt to scald the 
leaves that happen to be touching it. The wires forming the 
trellis are stretched horizontally from both ends of the roof, at 
about nine inches distant. 

Instead of studs screwed into the rafter, the horizontal wires 
may be fixed, and kept in their places, by rods of iron, having 
holes for the wires passing through, at regular distances. These 



86 



INTERIOR ARRANGEMENTS. 



rods are attached by a loop and staple to the front wall at the 
lower end, and to the back wall at the upper. This method is 
preferable to having the studs screwed into the rafter, as they 
can be easily removed, or the whole tegument of trellis may, 
if desired, be taken down and put up again without much 
trouble. This is of great importance on occasions of cleaning 
and painting the sashes, etc. Fig. 28, C, shows the perforated rod 
which is here referred to, the looped end being fixed in common 
staples. 

When provision is made for a middle trellis, this should 
always have a curvilinear shape, as in a, Fig. 29. This form 

Fig. 29. 




affords not only the largest training surface, but presents a 
larger surface to the light, than any other form that can be 
adopted, and, what is of more importance in regard to small 
houses, it occupies less room in proportion to its training surface 
than any other trellis with which we are acquainted. 

Cross-trellises, or horizontal upright trellises in the middle of 
the house, not only destroy the effect within, but are worse than 
useless. Where the house is of sufficient size to admit of a 
middle trellis, and a sufficiency of roof-surface to afford the cen- 
tre of the sashes to be kept clear of foliage, we should prefer 
having a sloping trellis on the back wall, and the centre bed 
occupied with dwarf standards, planted either in a straight or 
zig-zag line along the border, which, under good management, 
will be as fruitful as if trained on a trellis, while their appear- 
ance would be pleasing and handsome. Fig. 29 will convey a 
better idea of our method than by description. Fig. 30 shows 
the same system carried out in a double-roofed house. 

Trellises are now made generally of wire, as being cheaper 



INTERIOR ARRANGEMENTS. 



87 



Fig. 30. 




Fig. 31. 




and lighter than wood. Wire is in every way fitter for the 
purpose than wood, especially for roof trellising. The distance 
at which the wires should be placed apart depends upon the 
kind of trees to be trained to them. For grapes, the distance 
should be 12 or 14 inches ; and for peaches, nectarines, and 
small-wooded trees, not more than 8 inches. The distance of 
the wires of the roof trellis from the glass should not be less 
than one foot for grapes, and for peaches and other similar trees 
not less than ten inches. In properly constructed houses, there 
should always be a lower trellis, with the wires placed at double 
the distance of the others, for training the summer shoots to, to 
prevent the crowding of the vine branches when the trees are 
full of fruit, in order that there may not be a confusion of fruit 
and foliage. Vines, or, indeed, any other kind of fruit trees, 
should never be nailed to the wood of the house ; but, in all 
cases, trained at some distance from it, however little room there 
may be for that purpose. 



2. The interior of the green-house is generally provided with 
a stage in the centre, and shelves round the sides, on which the 



©8 INTERIOR ARRANGEMENTS. 

plants are arranged ; and this is the principal object which 
demands our attention. In single-roofed houses, the stage gen- 
erally rises towards the back wall ; but in span-roofed houses, 
which are surrounded by a path, the stage or platform rises 
from both sides, and meets in the middle of the house. 

It is a principle with some people to place the stage on the 
same angle as the roof, i. e., each shelf rising at an equal dis- 
tance from the plane of the rafters. This, however, is a bad 
rule, and, in cases where the roof is very steep, will make a 
wretched receptacle for green-house plants, No general rules 
can be laid down for the erection of the stage, as this will very 
much depend upon the form and size of the house. We might 
add, however, that the angle of the stage ought never to exceed 
the angle of the roof, but, if practicable, should be rather flatter 
than otherwise, to admit of larger plants being placed on the 
"upper shelves, which serve to give the house a larger and more 
effective appearance from the inside view. 

Green-houses intended for the growth of a promiscuous col- 
lection of plants, some of which may reach a considerable 
height, should have but few shelves on the platform, say three 
or four rises are quite sufficient, leaving the upper shelves, at 
least, twice the width of the others. This applies, also, to sin- 
gle-roofed houses. Many commit an error in making their 
stages not only too steep, but the shelves too narrow and too 
high, individually. The shelves of a green-house for displaying 
plants ought not to be less than one foot in width, this width 
increasing towards the top shelf, and not more than eight or 
nine inches in height from each other. 

Houses appropriated to the growth of small plants, as nurse- 
rymen's stock-houses, propagating, etc., may be staged much 
closer than this. These remarks chiefly apply to the green- 
houses of private individuals, and houses for the exhibition and 
arrangement of a general collection of plants. 

3. Conservatories, orangeries, and houses for the growth 
of the palm family, have pits, or more properly beds, in which 
plants are planted out. These beds are sometimes level with 
the floor, and sometimes raised above it, being enclosed by a 






INTERIOR ARRANGEMENTS. 



curb. The principles of culture in these houses being some- 
what different from the common green-house, it is necessary 
that they be arranged to suit the plants grown in them. 

The general form of conservatory beds is exactly that of the 
structure. If the house be a parallelogram, the bed has the 
same form, sometimes divided in the middle by a path, and 
sometimes surrounded by a path on both sides. These structures, 
when properly built and managed, are undoubtedly the means 
of conferring on lovers of gardening and flowers, enjoyment of 
the highest and purest character. When a fine conservatory of 
this kind is attached to the mansion house, or connected with it 
by a glazed arcade, it forms one of the most delightful prome- 
nades in winter that wealth and taste can command. 

There is undoubtedly much yet to be done in the way of 
improving the interior of ornamental conservatories, not only as 
regards their adaptability to plant culture, but also their general 
effect. We seldom see anything else than the same flat, formal 
bed or border, which is either rectangular, round, or square, 
according as the form of the building may determine by its 
walls. Even the refinement or elegancies of construction of 
architecture fail to invest such buildings with any character 
of distinctness or novelty, owing to the sameness or monotony 
which forms the basis of the design. As far as relates to the 
exterior, a considerable improvement is taking place from the 
use of curvilinear roofs, and lighter and more elegant workman- 
ship, and also resulting from the adoption of double-roofed 
houses, instead of the dark, dull, narrow, clumsy shed-like erec- 
tions which formerly used to be erected, and the various forms 
of elevation, which are now so generally arranged as to produce 
a very pleasing and picturesque effect. 

A recent and very general improvement in the construction 
of green-houses, consists in making the stages and shelves of 
slate, or thin plates of stone ; this practice is now common about 
London. These slates are frequently grooved or hollowed out 
so that the water is retained under the pots, and thus dripping 
is prevented, and evaporation is provided for in dry weather. 
This may be considered as a real improvement, which is proved 
by the readiness with which this practice was adopted by prac- 



90 INTERIOR ARRANGEMENTS. 

tical gardeners and nurserymen, and, from the cool nature of 
that material, deserves to be more extensively followed in orna- 
mental green-houses in this country. 

The irregular method of laying out the interior of conservato- 
ries, which promises to subvert the formal and monotonous 
arrangements of the old school, is one of the greatest steps 
towards a higher and more natural taste of artificial gardening 
than any other that has taken place in this department of the 
art for the last fifty years, inasmuch as it can be carried out 
with equal advantage on a large, as well as on a small, scale; 
and where this method is applied to a large structure, i. e., 
a structure covering a large area of ground, it necessarily leads 
to the adoption of interior arrangements, as far surpassing the 
old method in beauty and effect as it does in respect to econ- 
omy, convenience, and comfort. 

When we visit a conservatory lately erected, and see it to be 
a perfect fac simile of others that had been erected a century 
before, there is positively nothing to strike us with admiration, 
except, perhaps, the character of its architecture. When we 
see, in the costly erection before us, the exact image of conser- 
vatories everywhere else, the object loses one half of the charms 
of novelty and interest. It is, in fact, in the endless variety and 
intrinsic beauty of which they easily admit, that their chief 
fascination rests. This is the case with all other objects of art; 
with private mansions, for instance. How monotonous and tire- 
some would a country or suburb be, were every mansion and 
dwelling an exact copy of the other ! And why should it be so 
with erections for the growth of plants ? Why should these, 
which are, to a certain extent, invested with the charm of rarity, 
be deprived of the charm of variety ? Why should there not 
be groves, and lakes, and irregular flower beds, and rocks, and 
aquariums, and caverns, and jets, and waterfalls within as well 
as without ? In the former case, their beauties would be avail- 
able, either for recreation, admiration, or study, at all seasons ; 
in the latter, the fickleness and vicissitudes of our climate fre- 
quently prevent the enjoyment of either. 

The finest illustration of this system with which we are 
acquainted, is in the beautiful conservatory of the Royal 



INTERIOR ARRANGEMENTS. 91 

Botanic Society's Garden, in the Regent's Park, by Mr. Mar- 
nock, and which is, perhaps, one of the best adapted structures 
for the growth of plants in England, and is decidedly superior 
to the many monster plant-houses lately erected in that country. 
We have compared this structure with the large houses at 
Chatsworth, Kew, Sion House, and other places, and, whether 
in respect to convenience and comfort, general appearance or 
adaptability, we consider it in every way preferable to any other 
structure of the kind we have seen. This splendid winter- 
garden — for its great size justly entitles it to this name — 
contains collections of different degrees of hardiness, and em- 
braces climates suitable to each. Its walks are gravelled, like a 
flower-garden, winding through amongst the various groups of 
plants; sometimes overhung with the pendulous branches of 
flowering plants of great size and beauty, and sometimes wind- 
ing beneath arches and arbors of climbers in wild profusion. 
Here you climb over rocks, covered with characteristic plants, 
and there you descend into the humid recesses of orchids and 
aquatics. This house has not the domed and lofty character of 
some other structures of the kind, which is at once a prominent 
feature and a prominent fault in their construction ; it consists 
of several spans, supported on light iron columns, the centre one 
being somewhat higher than the others; and, though having 
little pretensions to what is generally called architectural dis- 
play, yet its commanding position and its magnitude strike the 
observer with a feeling of admiration, which is only surpassed 
by its internal arrangements. 

The general system of building conservatories in a recess 
of the mansion is entirely subversive of this method of internal 
arrangement, because of their total inadaptability for this pur- 
pose. It must not be supposed, however, that there is any abso- 
lute reason for detaching the conservatory from the mansion, if 
it be otherwise desired ; but it ought to be there as a positive 
part of the building, not a tributary attachment to fill up a cor- 
ner. That these kinds of structures for plants are being rapidly 
improved, is evident, and this, indeed, must be the case, since 
the improvement here spoken of springs from necessity. The 
attachment of a green-house to a mansion appears to us in as 



92 INTERIOR ARRANGEMENTS. 

questionable taste, as placing the conservatory in the middle of 
the kitchen garden, or in the orchard ; and if any kind of hor- 
ticultural structure is to be attached to the mansion, it ought, 
by all means, to be a conservatory. 

As an illustration that conservatories may form prominent 
portions of a mansion, or even a whole wing of it, without 
destroying its architectural character, we might point to a design, 
in the December number of the "Horticulturist" for 1849, by A. J. 
Downing, Esq., of Newburgh, which is introduced to show how 
a simple structure of this kind ought to be treated so as to give 
the whole an architectural and harmonious character, and show- 
ing, also, how this may be accomplished without rendering the 
conservatory opaque on either side, except the one end by which 
it is attached to the house, — a circumstance which will be 
indispensable in conservatories attached to houses, unless they 
be joined by means of a veranda, which gives them somewhat 
of an isolated character. This house which we have referred 
to is the kind of conservatory which we like, being satisfied, 
from experience, that, unless they be constructed somewhat 
after this method, they can never give the proprietors that satis- 
faction which they have a right to expect ; and we trust Mr. 
Downing will go on with creations of this kind, till these trans- 
parent conservatories become more general than they are at 
present. 

Although it is not necessary, on account of perfect adapta- 
bility, to place conservatories apart from dwelling-houses, yet 
we generally find that structures, standing detached from the 
mansion, are better suited for the growth of plants : first, because 
there is less temptation to introduce massive workmanship, on 
purpose to harmonize with the house ; and, secondly, there is, 
in most instances, more facility of making the house to satisfy 
the requirements of vegetation, and, consequently, less likelihood 
of departing from the principles of erection which science and 
practice have determined as essential to the successful cultiva- 
tion of plants. 

In many instances, it is absolutely impossible to comply with 
these principles, whatever interior arrangements may be adopted. 
Where the conservatory is a mere lean-to, stuck-in attachment, 



INTERIOR ARRANGEMENTS. 93 

compliance with the principle of plant-culture, or with the 
method of interior arrangement which we have here recom- 
mended, is equally impossible. In the latter case, the greater 
portion of the plant-house must necessarily be formed by the 
walls of the building, and the shadow of its elevated parts will 
be thrown upon the plant-house for at least one half the day. 
This is nearly as injurious as if the portions thus shaded 
were opaque. The only way of obviating the evils consequent 
upon its position, is to give every possible inch of light to the 
one, to enable it to counterbalance the shade which it must bear 
from the other. 

When plants are planted in beds in the conservatory, they 
require to be large specimens, otherwise they have a meagre 
appearance, and must be a great distance from the roof, and 
this is one of the greatest difficulties the gardener has to contend 
with. It must be borne in mind that fine specimens do not 
consist in plants that reach from the bed to the glass, with naked 
stems, and only a few branches at the top, which is invariably 
the result of lofty roofs and dark walls. 

"We have already shown, in the preceding section, the conse- 
quence of high-roofed houses, and the difficulty of managing 
them in a manner fitted for the successful cultivation of plants ; 
and if high-domed or right-lined roofs be improper in houses 
where the plants are elevated on shelves and stages, they are 
much more'so where the plants are set in the beds without pots, 
as the distance from the light renders it impossible for them to 
grow bushy and branching below. These, when included within 
the common-place curb of a square, or a parallelogram, or an 
oval, or circle, which are little better, (except when sparingly 
introduced, and only where they are described by the natural 
curves of the contiguous figures,) invariably produce an effect 
so common-place and uninteresting, as to fail in exciting the 
faintest emotions of pleasure, or novelty, or interest, in one out 
of a hundred individuals of taste and judgment. 



94 INTERIOR ARRANGEMENTS. 



REFERENCE TO FIG. 32. 

A, A, A, A, A, A, Beds in which the plants are set out and 

arranged according to their methods of growth, habits, 
height, &c. 

B, Water Tank, with jet in the centre. This tank is surround- 

ed by rock-work and characteristic plants. 

C, C, Seats on each side of the jet, commanding, also, views of 

the surrounding grounds. 

D, D, D, D, Conduit for the hot-water pipes, for warming the 

structure. This open conduit passes along the wall the 
whole length and breadth of the house, and is covered with 
grating, which serves as a path for watering, and conduct- 
ing the necessary operations connected with the culture of 
the plants. 
Ej E, E, an open Balcony, passing all round the house, and 
surrounded by a balustrade. This balcony forms a contin- 
uation of the porch on the one side, and runs out upon the 
ground-level on the other. From this balcony are seen 
the garden, the lakes, the hot-house, and the ornamental 
grounds. The chief purpose of this balcony, however, is 
to maintain the ground-level of the floor, and to make the 
conservatory in harmony with the mansion, without de- 
stroying its adaptability as a first-rate plant-house, of that 
class intended for growing large specimens, planted out in 
the ground. 

F, Steps, leading from the balcony into the pleasure-grounds. 

G, Door opening from the drawing-room. 

H, Rock-work for alpine plants, surrounding the aquarium and 

jet. 
For end view of this house, see Frontispiece. 



INTERIOR ARRANGEMENTS. 



95 



Fig. 32. 




96 INTERIOR ARRANGEMENTS. 

Conservatories are, probably, the most important structures 
used in ornamental gardening; and, as we have already said in 
regard to other kinds of horticultural buildings, we say, also, of 
them, that no degree of gardening ability, and practical attention 
on the part of the gardener, will compensate for the want of light 
and air; and, where the arrangements for the working of the 
house, in regard to air, heat, &c, are imperfect, the risk is great, 
and it is painful for a skilful and zealous gardener to contem- 
plate the consequences which he may be unable to prevent. 
One single night may destroy the labors of years past, and for- 
bid hope for years to come ; and, after all, the blame may be 
laid where it is least merited, and censure withheld from the 
party who most deserved it. 

In all buildings, and especially conservatories, the most com- 
plete and elegant design, when badly executed, is disagreeable 
to the view, defective in the object of its erection, and ruinous to 
the proprietor, because it is incapable of giving that satisfaction 
and pleasure which he was entitled to expect from his outlay. 

Fig. 32 is the ground plan of a conservatory, which we have 
designed for erection at a gentleman's country-seat. It is in- 
tended to form a prominent wing of the mansion. The structure 
is entered at one end by a door, leading from the principal 
apartments of the house. The conservatory is traversed by 
curved walks, laid with marble, and bordered by a curb, on each 
side, of the same material. In the centre is a basin of water, 
with a jet playing over a rockery, as seen in the cut, Fig. 32. 
In this design we have endeavored to combine perfect adapta- 
bility, with beauty in the structure, and harmony in the whole. 

This method of laying out the interior of a conservatory 
admits of the most perfect arrangement in the planting of the 
beds and compartments, intended for the exotic trees and shrubs, 
with which the structure is to be filled. The walks wind 
through, among the plants, as in a common shrubbery, or flower- 
garden ; and, when the compartments are tastefully arranged, 
and the whole kept in healthiness and luxuriance, with climbing 
plants hanging in festoons from the rafters and other supporters 
of the roof, it forms decidedly the most delightful and satisfac- 
tory kind of horticultural structure that can be erected for com- 
fort, convenience, and enjoyment. 



INTERIOR ARRANGEMENTS. 97 

We do not think that any definite rule can be laid down for 
the laying out of the area of a conservatory, as the formation of 
the beds and walks may be dictated by the taste of the proprietor, 
or those in whom he confides the management of the Work. 
Almost any curve may be adopted in the walks, without destroy- 
ing the effect of the interior view. What we condemn is the 
monotonous straight lines by which the area is generally laid 
out. It must be observed, however, that this method is entirely 
inapplicable, unless the house be glazed on at least three sides, 
and the roof so constructed as to admit the greatest possible 
quantity of light in proportion to the extent of the area enclosed. 
The roof should, also, be as low as is consistent with exterior 
effect, and the admission of plants of good size ; for, as we have 
already observed, one of the prevailing errors in the construction 
of conservatories adjoining mansions consists in their being 
made too lofty and too opaque. They are designed generally to 
suit the place of the building, without regard to the effect of the 
conservatory itself, as a structure, or as a plant-house. 

There are many other advantages, resulting from houses of 
this description, which, in a practical point of view, are deserv- 
ing of consideration. Not the least of these is the facility with 
which plants can be arranged to produce the best possible effect. 
Plants are much easier arranged within curved lines, than in 
squares or parallelograms ; and the curvatures of the beds are 
always more spirited and pleasing than continuous straight 
lines, whatever the house may be filled with, or however badly 
the plants may be disposed. 

We have only room to notice one feature more in the con- 
struction of this conservatory, viz., the form of the roof. We 
have chosen the spans of different sizes, in preference to one 
single span, as much for adaptability as to harmonize with the 
architecture of the mansion. This system tends to prevent the 
accumulation of warm air at the top of the house, and hence 
the heat is distributed more equally among the plants. For the 
same reason, ventilators are provided at the top of each span, so 
that the external air admitted, as well as the artificial heat ris- 
ing upwards, will be more equally distributed over the housed 

* For further notice of this, see Ventilation. 



98 INTERIOR ARRANGEMENTS. 

An end view of this structure is shown in the frontispiece. As 
the ground, in this case, descends gradually from the base of the 
mansion, a considerable depth of parapet wall is necessary to 
bring the floor of the conservatory to the desired level, and the 
requisite distance from the roof. Curved roofs can only be 
adopted where the building admits them without jarring dis- 
cordantly with the general architecture, and, in some instances, 
straight-lined roofs will be preferable ; but in all cases where 
curvilinear roofs can be made to harmonize with the building, 
they are decidedly to be preferred, on account of the superior 
beauty of curved lines viewed in contrast with the surrounding 
seenery, and also on account of the superior beauty of the struc- 
ture from within, in harmony with curved figures of the walks 
and borders of a house, such as that we have here described. 



SECTION V. 

MATERIALS OF CONSTRUCTION. 

1. Workmanship. — However excellent and adaptable may- 
be the design of a horticultural erection, if the work be badly 
executed the structure will generally be defective in the work- 
ing, and the trouble of management will be greatly increased. 
Bad foundations, bad roofs, bad-fitting sashes, rendering them 
difficult to open and shut, bad glazing, and bad workmanship of 
even* description, are too common to exist without being a very- 
perceptible evil, and one that is much complained of by practical 
gardeners, upon whom the consequences of this method of con- 
struction generally fall. In all regular work, coming under the 
province of the architect or engineer, there is generally particu- 
lar attention directed to the facility of working, and ingenuity- 
is exerted to its utmost limits to perfect and simplify those 
facilities, however temporarily the structure or work may be 
constructed. But horticultural buildings, relatively to civil 
architecture, appear to be an anomalous class of structures, not 
coming strictly within the province of the architect, — except 
in so far as they may be related to the house in an architectural 
point of view, — and hence they are more the subject of chance 
or caprice in design, and of local convenience in execution, 
than any other department of rural architecture. The subject 
of horticultural architecture has not been deemed of sufficient 
importance to induce civil architects to make themselves ac- 
quainted with the principles on which plant-houses should be 
constructed, or to consider the nature of workmanship in relation 
to its work ; and, consequently, the construction of horticultural 
buildings is either left wholly to gardeners, who understand 
little of the science of architecture, or wholly to architects, who 
understand as little of the science of horticulture. The conse- 
quence, in either case, is generally incongruity in appearance, 
9* 



100 MATERIALS OF CONSTRUCTION. 

want of success in the useful results, and want of permanency 
in the structure itself. In every country, no doubt, such cases 
are numerous, but here, they are more numerous probably than 
in any other, arising, no doubt, from that want of attention to 
the details of horticultural architecture, and to the still unde- 
veloped principles of science, upon which it is based. 

The temporary and inferior character of the workmanship 
generally bestowed on horticultural erections is a source of great 
loss to those erecting such buildings, and demands the serious 
attention of all who contemplate the construction of them. The 
remarks, which have been applied by a popular writer on farm- 
ing in regard to farm-buildings, are still more applicable to build- 
ings for the purposes of horticulture.^ Buildings, manifestly 
intended to be permanent, are put up to stand for a year or two, 
when it becomes absolutely necessary to their continuation, to 
spend a sum upon them equal to one third the cost of their 
original erection, which acts as a drawback upon the progress 
of horticulture in this country, as many suppose that this early 
additional expenditure is merely the consequence which the com- 
mon tear and wear of time entails upon all such structures ; and 
hence they are considered too expensive to keep in order, even 
though willing to go to the cost of original construction. Now 
experience has taught us that structures, substantially con- 
structed at the first, and of good materials, will stand for at least 
twenty years without any additional outlay, save a few coats of 
paint during that period, which increases their durability, the 
oftener it is applied. 

We have been induced to dwell longer on the subject of 
workmanship, from the numerous examples which have come 
under our own observation, and from the trouble and annoyance 
to which we are almost daily subjected on this account. In 
small erections, the inconveniences arising from bad workman- 

* Few things serve better to distinguish the habits, and even the 
characters, of the progeny from the parent stock, — the Americans from 
their English ancestors, — than the more perfect and durable character 
of all their mechanical works, machinery, and buildings. There, things 
are made to endure ; here, they are made to answer the purposes of the 
day. — [Ed. Farmer's Library.] ± 



MATERIALS OF CONSTRUCTION. 101 

ship may be little experienced ; but where the structures are 
large and extensive, the results become of the deepest impor- 
tance, in an economical point of view. 

It is not easy to point out a course wherein these difficulties 
may be avoided, or to discover, at all times, to whom blame is 
attributable. Tradesmen, who take the work by contract, prob- 
ably endeavor to do the best they can with the job they have 
taken in hand, and it is generally their policy to get over it as 
easily and as quickly as possible. Gardeners who may have 
the superintendence of the work, probably do the best they can, 
but from their wanting the necessary knowledge of the details 
of construction, are unable to exercise that surveillance which is 
necessary to the proper execution of the work. 

2. Materials of the Frame of the Building, tyc. — The most 
suitable material for the frames of horticultural buildings has 
lately been made the subject of considerable discussion and ex- 
periment, which has not been without its use in the elucidation 
of facts hitherto unknown, or, at least, unnoticed in general 
practice. The case of w T ood versus iron has been investigated 
on various grounds, by practical and scientific men, without, 
however, coming to a unanimous decision on the superiority of 
either. In this matter, as in some others like itself, some have 
adopted extreme views of the various merits and defects of the 
different materials, and have come to their conclusions by refer- 
ence to some single or specific property. These views and con- 
clusions, however, have been of considerable utility in bringing 
the subject before the bar of unbiased inquiry, which, if it has 
not already done so, is likely to result in the adoption of modi- 
fied views, and the recognition of specific principles, that, when 
fully considered and duly weighed against each other, will ulti- 
mately lead to a more definite result. 

The use of iron in the construction of hot-houses, like every 
other really valuable improvement, has met with much opposi- 
tion from the still slumbering spirit of prejudice, whieh is gener- 
ally slow to believe in the superiority of anything different from 
that with which it has been long acquainted, even when this 
superiority cannot, on reasonable grounds, be denied. This 



102 



MATERIALS OF CONSTRUCTION. 



spirit, however, which has long held undisputed sovereignty 
over the minds of gardeners, is fast giving way before the sweep- 
ing current of mechanical inventions ; and when science comes 
to the aid of mechanism in the building of hot-houses, as in the 
erection of factories, steam-engines, and other works of art, then 
the flimsy barriers reared by prejudice will be swept away, and 
I think I may fearlessly assert that, in regard to the opposition 
that has been given to the erection of iron hot-houses, this has 
nearly taken place. 

Gardeners, from the early ages of Abercrombie and Nicol, 
have been prejudiced against metallic hot-houses, and, to our 
knowledge, this prejudice is still entertained by some whose 
learning and intelligence would encourage us to look for more 
accurate judgment. 

The objections which have been raised against metallic houses 
for horticultural purposes, are chiefly the following : — 

Contraction and expansion, oxydation, abduction of heat, at- 
traction of electricity, and original cost. 

In regard to the first, and principal cause of opposition, viz., 
its susceptibility to the influences of heat and cold, a fact which 
cannot be denied, yet it is proved by experience that if a house 
be properly constructed of good material, this susceptibility is 
of no practical importance. In very small houses the incon- 
venience occasioned by sudden fluctuations of temperature may 
be more sensibly felt, although, in the management of small iron 
vineries, in England, we have never seen the slightest incon- 
venience result from external changes ; indeed, all our expe- 
rience in the management of hot-houses goes to prove the 
superiority of iron over wood, for every purpose to which timber 
is generally applied. It has been stated that metallic roofs are 
more liable to break the glass than wood ; practice has also 
proved that this statement is without foundation, and if it has 
ever taken place, can only be in copper or compound metallic 
roofs. Cast-iron or solid wrought-iron bars have never been 
known to cause breakage of glass, or displacement of joints, and 
some have asserted that the breakage of glass is even more, 
during sudden changes, by wood than by iron roofs. 

The expansibility of copper being greater than that of iron, 



MATERIALS OF CONSTRUCTION. 103 

in the proportion of 95 to 60, therefore copper is above one third 
more likely to break glass than iron. But when it is considered 
that a rod of copper expands only xosWf part of its length with 
every degTee of heat, and that iron only expands ye-g^er P ar ^> 
the practical effects of even the hottest portion of our climate 
on these metals can never amount to a sum equal to the expan- 
sion required for the breakage of glass. 

The second objection which we have mentioned is also unde- 
niable. All metals are liable to rust; but painting easily rids us 
of this objection, at least it will so far prevent it as to form 
hardly any objection. 

The power of metals to conduct heat is an objection which, 
like the others, cannot be denied, but may be partially obviated. 
The abduction of heat, like the expansibility of metallic roofs, 
is very little felt in using them ; the smaller the bars, the less 
their power of conduction. The paint, also, and the putty used 
to retain the glass, obviate this objection. Heat may be supplied 
by art, but light, the grand advantage gained by metallic bars, 
cannot, by any human means, be supplied but by transparency 
of roof. 

The objection raised on the ground of attraction of electricity, 
is easily answered. If metallic hot-houses and conservatories 
attract electricity, they also conduct it to the ground, so that it 
can do them no harm. What is corroborative of this position 
is the fact, that no instance has come under our knowledge of 
iron hot-houses having been injured by the electric fluid. 

The objection regarding the expense of iron hot-houses, has 
been sufficiently refuted in England, and we have observed, 
with pleasure, a refutation of the same objection, by an enter- 
prising gentleman of Cincinnati, who has lately erected an iron- 
roofed vinery. Mr. Resorr has given a cut, and description of 
this house, in the " Horticulturist " for Sept. 1849, p. 117. This 
is the only substantial account we have seen of the comparative 
cost of iron and wood roofs. This gentleman, who is in the 
foundery business, has every opportunity of knowing the accu- 
rate cost of such a house, and plainly states, " that those wish- 
ing to build a good, substantial house, can do it, and make the 
roof of iron, as cheaply as of wood, the other parts costing the 



104 MATERIALS OF CONSTRUCTION. 

same." From inquiries and calculations which we have made, 
we have come to the same conclusion, although, from a want 
of the requisite knowledge, and from the expense of having 
patterns made for the castings, it may, in some localities, cost 
more than a structure of wood. 

In small houses, sudden changes of the external temperature 
are much sooner and more sensibly felt than in large structures, 
whether they are constructed of wood or iron, which arises from 
the fact that the smaller volume of air confined within becomes 
more rapidly heated, and hence the change is the sooner felt. 
Supposing the circumstance to be more strikingly sensible in the 
case of small iron houses, — then all that is necessary to coun- 
terbalance it, is just a little more attention to ventilation, during 
sudden changes of external temperature. 

For large structures iron is incomparably superior to wood, 
and even for forcing-houses we would decidedly prefer the same 
material. The contraction and expansion of metallic hot-houses 
may be dreaded in the Southern States, if built on a very small 
scale, and badly managed ; but in structures of moderate size, 
this evil will be found practically of little importance, unless 
they are badly constructed, and negligently managed. 

The finest horticultural structures that have yet been erected 
in Europe are made of iron, and no houses of any importance 
are now being erected of wood, which proves its superiority over 
the latter material. The great conservatory, or Palm-house, 
at Kew, is wholly of iron, constructed under the auspices of the 
most scientific men in England. The Botanic Society's conser- 
vatory, in the Regent's Park, (already spoken of,) is made of 
iron. The fine plant-houses in the Glasnevin Botanic Garden, 
near Dublin, are constructed of iron, and the quite unequalled 
range of forcing-houses at Frogmore, in Windsor Park, are also 
of iron. In fact, the most extensive horticultural erections in 
Europe are made of iron, and many others, now in course of 
erection, are being made of the same material. 

Admitting that properly constructed iron houses would cost, 
at the outset, somewhat more than wooden ones, their lightness 
and elegance render them much superior in point of appearance, 
and, when their durability is taken into consideration, they will, 



MATERIALS OF CONSTRUCTION. 105 

undoubtedly, be found cheaper in the end. But the cost of con- 
struction will vary, according as the details are understood by 
the constructors ; for if Mr. Resorr can make a vinery of iron as 
cheaply as of wood, then other tradesmen, when they have prop- 
erly understood the nature of the work, will surely be able to 
do the same. The Palm-house at Kew was constructed by a 
tradesman from Dublin, while some of the most extensive hot- 
house builders in England lived within the sound of their ham- 
mers, and the material and workmen were all brought across the 
channel, costing nearly as much as if brought to America ; yet 
the workmanship was superior, and the cost said to be less, — 
proving that practice and knowledge of the details lessen the 
original cost of construction.* 

* As instances of comparatively easy transportability of iron hot- 
houses, we might mention, that the whole of the materials of the 
immense structure at Kew were manufactured and fitted together at 
Dublin, and transported from thence to London. The unequalled range 
of forcing-houses at "Windsor, one thousand feet in length, was made at 
Birmingham, and fitted together in the works, before they were trans- 
ported to their final destination. Is ow it would have been just as easy, 
and perhaps little more expensive, to have shipped them to Isew York, 
or Boston, or Philadelphia, or Baltimore. When this is done in England. 
how long will American enterprise be behind them ? "We prophesy, not 
long. 



SECTION VI. 

GLASS. 

1. Experiments which have hitherto been made, in regard to 
the physical properties of glass as a transparent medium, have 
been conducted, generally, on purely chemical principles, and 
mostly without reference to observed facts, as regards the growth 
of plants, excepting, perhaps, those of the most common and 
obvious character. Partly for this reason, and partly from care- 
less negligence, hot-houses have long been, and still continue 
to be, glazed with material of a very inferior description. If 
any one doubts this, let him look at some of the finest hot- 
houses in the country, and he will easily perceive the truth of 
this statement ; the sickly and scorched appearance of the 
plants under its influence, being far more painful than agreeable 
to the eye of any one who takes an interest in the vegetable 
kingdom. This evil, alone, renders the very best cultivation of 
no avail. 

The most elaborate and practically useful investigations that 
have yet been made, in this department, are those lately under- 
taken, with the view of securing the very best material that 
science and art could produce, for the glazing of the great Palm- 
house at Kew. We cannot do better than present our readers 
with the following extract from Mr. Hunt's report to the com- 
mittee, which we take from Silliman's Journal of Science and 
Art, vol. iv., p. 431. 

" It has been found that plants growing in stove-houses, often 
suffer from the scorching influence of the solar rays, and great 
expense is frequently incurred, in fixing blinds, to cut off this 
destructive calorific influence. From the enormous size of the 
new Palm-house, at Kew, it would be almost impracticable to 
adopt any system of shades that would be effective, this building 
being 363 feet in length, 100 feet wide, and 63 feet high. It 



GLASS. 107 

was, therefore, thought desirable to ascertain if it would be pos- 
sible to cut off these scorching rays by the use of a tinted glass, 
which should not be objectionable in its appearance, and the ques- 
tion was, at the recommendation of Sir William Hooker and 
Dr. Lindley, submitted, by the commissioners of woods, &c, to 
Mr. Hunt. The object was to select a glass which should not 
permit those heat rays, which are most active in scorching the 
leaves of plants, to permeate it. By a series of experiments, made 
with the colored juices of the palms themselves, it was ascer- 
tained that the rays which destroyed their color belonged to a 
class situated at the end of the prismatic spectrum, which ex- 
hibited the utmost calorific power, and just beyond the limits of 
the visible red ray. A great number of specimens of glass, vari- 
ously manufactured, were submitted to examination, and it was 
at length ascertained, that glass tinted green appeared most likely 
to effect the object desired, most readily. Some of the green 
glasses that were examined, obstructed nearly all the heat rays ; 
but this was not desired, and, from their dark color, these were 
objectionable, as stopping the passage of a considerable quantity 
of light, which was essential to the healthy growth of the plants. 
Many specimens were manufactured purposely for the experi- 
ments, by Messrs. Chance, of Birmingham, according to given 
directions ; and it is mainly due to the interest taken by these 
gentlemen, that the desideratum has been arrived at. 

" Every sample of glass was submitted to three distinct sets of 
experiments. 

" First. — To ascertain, by measuring off the colored rays of 
the spectrum, its transparency to luminous influence. 

" Second. — To ascertain the amount of obstruction offered to 
the passage of the chemical rays. 

" Third. — To measure the amount of heat radiation which 
permeated each specimen. 

" The chemical changes were tried upon chloride of silver, and 
on papers, stained with the green coloring matter of the leaves 
of the palms themselves. The calorific influence was ascer- 
tained by a method employed by Sir John Herschel, in his ex- 
periments on solar radiation. Tissue paper was smoked on one 
side, by holding it over a smoky flame, and then, while the 
10 



108 GLASS. 

spectrum was thrown upon it, the other surface was washed 
with strong sulphuric ether. By the evaporation of the ether, 
the points of calorific action were most easily obtained, as these 
dried off in well defined circles, long before the other parts pre- 
sented any appearance of dryness. By these means it is not 
difficult, with ease, to ascertain exactly the conditions of the 
glass, as to its transparency to light, heat, and chemical agency, 
(actinism.) 

" The glass thus chosen is of a very pale yellow green color, 
the color being given by oxide of copper, and is so transparent 
that scarcely any light is intercepted. In examining the spec- 
tral rays through it, it is found that the yellow is slightly dimin- 
ished in intensity, and that the extent of the red ray is diminished 
in a small degree, the lower edge of the ordinary red ray being 
cut off by it. It does not appear to act in any way upon the 
chemical principle, as spectral impressions, obtained upon chlo- 
ride of silver, are the same in extent and character as those 
procured by the action of the rays which have passed ordinary 
white glass. This glass has, however, a very remarkable action 
upon the non-luminous heat rays, the least refrangible calo- 
rific rays. It prevents the permeation of all that class of heat 
rays which exists below, and in the point fixed by Sir William 
Herschel, Sir H. Englefield, and Sir J. Herschel, as the point 
of maximum calorific action, and it is to this class of rays that 
the scorching influence is due. There is every reason to con- 
clude that the use of this glass will be effectual in preserving 
the plants, and at the same time that it is unobjectionable in point 
of color, and transparent to that principle which is necessary for 
the development of those parts of the plant which depend upon 
external chemical excitation, it is only partially so to the heat 
rays, and it is opaque to those only that are injurious. The 
absence of the oxide of manganese, commonly employed in all 
sheet glass, is insisted on, it having been found that glass, into 
the composition of which manganese enters, will, after exposure 
for some time to intense sun-light, assume a pink hue, and any 
tint of this character would completely destroy the peculiar 
properties for which this glass is chosen. Melloni, in his in- 
vestigations on radiant heat, discovered that a peculiar green 



GLASS. 109 

glass manufactured in Italy, obstructed nearly all the calorific 
rays. We may, therefore, conclude that the glass chosen is of 
a similar character to that employed by the Italian philosopher. 
The tint of color is not very different from that of the old crown 
glass, and many practical men state, that they find their plants 
flourish better under this kind of glass, than under the white 
sheet glass, which is now so commonly employed." 

We understand the glass employed in the Kew Palm-house 
has fully answered the intended purpose, viz., of obstructing the 
most injurious portion of the heat rays ; and we have learned, 
also, that it has answered all expectations as to its influence on 
the health of the plants, although its perfect utility, in this 
respect, has been doubted by some practical men. We think, 
however, that an absolute decision on its merits, in this respect, 
is rather premature, as we should prefer seeing the plants attain 
a greater size, so as to fill the structure more completely, and 
their foliage reach nearer to the glass, before pronouncing defi- 
nitely upon the calorific effects of the latter. 

As to the appearance of this glass, it is altogether a matter 
of taste, which we consider ourselves having no right to ques- 
tion ; and, upon the whole, w T e think it in this respect unob- 
jectionable. When viewed obliquely, from a distance, it is 
slightly green, but when viewed from within, and at right 
angles to its surface, it is clear and nearly white. This kind 
of glass is highly worthy of the attention of glass-makers and 
horticulturists in this country, and we have no doubt, when its 
qualities have been fairly tested and made known, it will be 
extensively employed in horticultural buildings. 

No kind of economy is more sure to defeat its end than 
using cheap glass in horticultural structures. Many suppose, 
if a house is merely covered with glass and made transparent, 
that all is well. We know this to be a common opinion ; yet 
we are fully prepared to prove its falsity, not by mere assertion, 
but by indubitable facts, — facts so clear that the most ignorant 
in these matters will be convinced, from his own observation, 
and on a scale so extensive, as to justify the conclusions that 
have been drawn from them. 

We know of nothing connected with the erection of horticul- 



110 GLASS. 

tural buildings so vexatious as having the roof glazed with 
bad glass ; plants of almost every kind are certain to suffer 
under it. Knotted and wavy glass is the worst of all, as the 
knots and waves form lenses, and concentrate the sun's rays 
upon the plants, and that part on which the concentrated ray 
falls is sure to be burnt. It cannot for one moment be doubted 
that the glass used in the majority of horticultural buildings is 
not only inferior, but is of the very worst description ; and, on a 
recent examination of one hundred houses, we found scarcely 
one free from the defects here spoken of. Indeed, we are fully 
aware of the difficulty of procuring really good glass, at reasona- 
ble prices, for glazing hot-houses. But there cannot be a doubt 
that the money saved is money lost ; and if the vexation and 
annoyance subsequently incurred by the use of inferior glass, be 
taken into consideration, few persons of sound judgment will 
hesitate in paying an increased price. 

No doubt many of our readers will suppose that we are 
unnecessarily particular on this point, but our experience has 
taught us a severe lesson, and one, too, which no doubt has 
been strongly impressed upon the mind of every gardener, of 
lengthened experience in these matters. Against such an evil 
there is but one resource, — and a bad one it is, — which is 
shading, either by means of cloth blinds, or by painting, the 
worst method of the two; but the one or the other is absolutely 
necessary. The first is troublesome, the other is unsightly; 
and, to be done right, both are expensive. We have a large 
house now under our management, on which the glass is so bad 
as to render its opacity absolutely necessary to prevent burning, 
even when the sun's rays have lost their meridian power. 

In very small houses bad glass may be used with less chance 
of injury, as they may be easily shaded with blinds during the 
noonday sun ; but in very large structures this is only accom- 
plished at very great expense ; and in curvilinear houses, and 
houses with irregular roofs, covering them with blinds is almost 
impossible. Painting the glass, then, is the only resource, 
unless glass be used which does not require it. 

Little has been said on the effects of glass used in hot-houses, 
by writers on practical horticulture. Although facts are obvious 



GLASS. Ill 

and familiar in regard to it, yet the evils seem to be passed over 
as results which cannot be prevented. We can at this moment 
point to houses standing side by side, in one of which it is 
impossible to grow, and keep in health, any species of vegeta- 
tion whatever, — no matter how hardy the tissue of the foliage 
may be, — without shading the glass almost to opacity ; while, in 
the other, plants with tender and delicate foliage stand compar- 
atively uninjured. The cause is obvious : the glass with which 
the one is glazed is full of waves and blotches, and altogether 
of the worst description ; while that of the other, though not the 
best, is yet of better quality. The poorer glass burns vegetation, 
even when the incidental angle, between the impinging ray and 
a perpendicular to the roof, is as much as 45°. 

From what has been already said regarding the influence of 
the different solar rays on vegetation, and, more especially, the 
experiments made with regard to the Palm-house at Kew Gar- 
dens, by which it has been found possible to manufacture glass 
which is opaque to the scorching rays, without at the same time 
obstructing the light, heat, and chemical rays which are essen- 
tial to the development of plants, there can be no doubt that 
the scorching of vegetation in hot-houses, which has long been 
a serious drawback in exotic horticulture, can be prevented. 
And when more extended experiments have been made, a good 
material for glazing can undoubtedly be manufactured at a price 
that will insure its universal adoption in horticultural structures. 
It is to be earnestly desired that some of our enterprising manu- 
facturers, — a class so remarkable for their fertility of invention, 
— will take up the matter seriously , and supply us with the 
material which exotic horticulture so much requires. 

2. Glazing. — Common sash-glazing is generally performed 
with a lap of from one to three fourths of an inch, and, by many, 
with a full inch lap. This is a most objectionable method, as 
the broader the lap the greater the quantity of water retained 
in it by capillary attraction, and, consequently, the greater the 
breakage of the glass ; for when the internal temperature falls, 
and this water becomes frozen, the glass is certain to crack in 
the direction of the bars. The lap should never be broader than 
10* 



112 GLASS. 

a quarter of an inch, but where the panes or pieces of glass are 
not above five inches wide, one eighth of an inch is sufficient. 
Half an inch in roof-sashes, unless they are placed at an angle 
of not less than 45°, is almost sure to produce breakage, except- 
ing the temperature within be kept sufficiently high to prevent 
the water retained between the panes from freezing. 

Broad laps are objectionable, also, on other accounts ; for the 
broader the lap the sooner it fills with earthy matter, forming 
an opaque space, and these spaces are so numerous as to have 
a very considerable effect upon the transparency of the roof, 
which is injurious by excluding the light, and is also unsightly 
in appearance. It may be puttied, but its opacity is the same, 
and its appearance no better than if filled with dirt. Where 
the lap is not more than one fourth of an inch, it may be puttied 
without any very disagreeable effect, but if the glass be per- 
fectly smooth in the edges, puttying is useless, and the glass is 
better without it. 

The most approved practice as to the laps, whether in roofs 
or common sashes, is, to make the breadth of the lap equal to 
the thickness of the glass, leaving it entirely without putty. 
But it is extremely difficult to get glaziers to attend to this, and 
it can only be obtained by employing good workmen, and keep- 
ing strict supervision over the work. This is not only the most 
elegant of all modes of glazing, but the safest for the glass, 
which, as we have observed, is seldom broken by any other nat- 
ural means but the expansion of frozen water retained between 
the laps. This mode is also by far the easiest to repair, and is 
more durable than any method of filling the laps with putty, or 
with lead. 

There are various other modes of glazing, as the lead and 
copper-lap methods, which, however, are so very objectionable 
as to be unworthy of occupying space in our description. The 
methods of shield glazing are equally objectionable, and little 
used. Curvilinear glazing has been used somewhat extensively, 
and is, in the opinion of some men of undoubted skill, superior 
to the other methods already spoken of. 

Curvilinear lap-glazing appears preferable to the square mode, 
for various reasons, one of which is, that the curve has a ten- 



GLASS. 113 

dency to conduct the water to the centre of the pane, which is 
let out by a small opening at the apex of it. If the lap is broad, 
however, the water is accumulated by attraction precisely in the 
point where it is calculated to do most injury, — acting, in fact, 
as a power on the end of two levers of the second kind. But 
when the lap is not more than one sixteenth of an inch in width, 
no evil of this sort can happen. 

It ought to be borne in mind that puttying, or otherwise fill- 
ing up the laps, is in no case necessary if care be taken of the 
glazing, and smooth glass be used, and if the lap never exceeds 
one fourth, nor falls short one sixteenth, of an inch. However 
careful the laps may be puttied, in a very few years the putty 
begins to decay by absorption of moisture, and, when evapora- 
tion is great within, it becomes saturated with water, which 
readily freezes in frosty nights, (unless the temperature of the 
house is adequate to prevent it,) and breakage of glass is inevi- 
table. 

Reversed curvilinear glazing consists in making the lower 
edges of the panes to curve inwards, in a concave form, instead 
of curving outwards, in the common way. The effect of this 
method is the throwing of the condensed moisture down upon 
the bars, and thus conveying it off at the bottom of the roof, 
which prevents the moisture from being retained in globules, 
and dropping down upon the plants. This method is nothing 
more than reversing the position of the panes in common curvi- 
linear glazing, and is; according to our opinion, preferable to it. 

These are the most common and approved modes of glazing, 
although some others have been used that have not proved 
worthy of general adoption. Ridge-and-furrow roofs may be 
glazed in the same way. The size of the panes used makes no 
difference, — large ones only tending to reduce the opaque sur- 
face. Anomalous surfaces may be glazed with panes according 
to the figures of the bars. 

3. Color of Walls. — The color usually applied to hot-houses 
is white. As affording the finest contrast with the plants in the 
interior, and the vegetation around the outside of the house, the 
general taste is manifestly in favor of this color ; and, as it is 



114 



B! LSS 



the best reflector of light, it is, also, on that account, preferable 
\ other. TheTQ avo some considerations, however, in favor 
.•ark color, which, as has Ivon already stated, absorbs a 
larger oiiantity of" heat, and parts with it again en the cooling 
of the Atmosphere. A yellow .o'er we consider the most objec- 
tionable of all, both o - contrasting badly with the 
glass of the house and the verdure of vegetation, as well as the 
affects produced by it on the light, which, as will lv seen t'rom 
the preceding investigations, exercises an injurious intluence on 
vegetation, The intluence may not be so great in the reflected 
light, as when permeating yellow or orange-colored media, but 
the power is, nevertheless, exercised to some extent. The same 
investigations show the beneticial inti. I blue, or dark 
color, which perfectly accords with our observations on • 
giowi St dark bodies, otherwise exposed to abundance 
of light; and. when it is in accordance with the taste of the 
proprietor, we think the interior walls ot" hot-houses should be 
of a dark color. 

En England, where the rays ot' light are less powerful than 
here, dark-colored walls are now \c.y common [here, i 9 
a more important consideration than heat : the latter can be 
applied by artificial means; — not so the termor. This probably 
lends ta prevent the adoption of a dark color tor the interior ot' 
their hot-houses. Here, dark walls are more desirable than 
white - absorb the heat-rays, during a powerful sun, and 

prevent the a: - becoming so rapidly hot. This 

fact is sensibly felt on standing before walls ot' the different 
colors during the mid-day sun. By a white wall, the rays are 
reflected t'rom the wall bach into the air, or on any other body 
which - . bj which the temperature ot' the air and the 

Based, A dark-colored wall, on the con- 
trary, retains the heat which falls on its surface ; and though it 
.. .older, it contains more latent heat, which it only parts 
with when it is abstracted by the reduced temperature of the 
atmosphere. This, alone, is ;ament in favor of dark- 

colored walls in lean-to hot-houses. 

The inner side of the rafters, astragals, and sash-bars, should 
approach to the color of the glas*. As the light-rays e. 



GLASS. 115 

fall on them, nothing is gained by making them dark, and it 
gives the house a heavy and gloomy effect. The structure is, 
or should be, transparent. The impression on the mind is 
that of a house covered with glass; and, as the rafters and 
astragals are only there as supports to the glass, they should be 
deprived, as much as possible, of their opaque character. When 
they are painted a dark color, the reverse effect is produced. A 
glaring white color is, also, objectionable ; it is hurtful to the 
eye, and generally displeasing to a refined taste : some of the 
different shades of cream, or light stone color, will be more 
effective and pleasing. The same may be said in regard to the 
external portions of the roof. It may, by way of contrast, be a 
shade or two darker than the interior; but a decidedly dark 
color should be avoided. We have seen various plant-houses 
painted dark, and even dark red, but have seen very few who 
admired them. We do not wish to incur censure by finding 
fault with the taste of those who may fancy these colors, and 
admit that every one has an undoubted right to gratify his 
own taste. We give our opinions for the benefit of those who 
may choose to adopt them. 

It is a good plan to give the wood-work of the structure a 
coat of some anti-corrosive paint before the color is put on. The 
timber is preserved much longer ; and the house requires less 
painting, as the timber is hardened, and more impervious to 
moisture. For numerous preservative solutions, see Table 
XVIII, Appendix, 



SECTION VII. 

FORMATION OF GARDENS. 

1. Form of the Garden. — The form of the garden must be 
determined by two conditions : first, the natural disposition of 
the ground chosen for its site ; and, secondly, by the aspect and 
position of the walls and hot-houses. If there are no hot-houses 
or walls, the form of the garden will be regulated mainly by the 
first condition. In most kitchen or culinary gardens, of any 
importance, if no walls are erected, wooden palings are generally 
substituted for them, which also regulate the disposition of the 
ground. The site having been fixed upon, with due regard to 
the considerations necessary in choosing the site for horticultu- 
ral structures, (see Sect. I,) these considerations being in both 
cases equally applicable, the next thing to be done is the dispo- 
sition and formation of the walks, which also define the size 
and shape of the borders and principal compartments of the 
garden. 

2. Walks. — The principal walks from the house to the 
garden should be somewhat broader than the garden walks, and 
should, if possible, enter the garden at the south side. This is 
more especially desirable if there be hot-houses on the south 
side. In either case, however, it is desirable, as a more favor- 
able impression is produced on the mind of the spectator than if 
entering at either side. The north side is the very worst for 
the principal entrance, as the necessary offices connected with 
the garden, — the mould-heaps, rubbish-piles, manure, &c, — 
are generally located in that quarter; besides, the impression, 
produced by the best trained trees on the walls or fences, and 
the general view of the ground, is lost. Next to the south, the 
east or west sides should be chosen. 

There are various methods of forming walks, according to the 



FORMATION OF GARDENS. 117 

character of the soil and sub-soil, and the kind of material at 
hand to form a surface. Where the ground is naturally wet, or 
where there is a liability of the accumulation of water, the soil 
should be taken out to the depth of at least twenty inches, — 
the section formed by the excavation forming an obtuse angle 
towards the centre, or forming the segment of a circle. These 
excavations should lead into drains, at the lowest points, to carry 
off the water that percolates through among the stones with 
which they are filled. They may be filled to within two inches 
of the intended surface of the walk, — the largest in the bottom, 
and the smaller toward the surface. This forms a durable and 
dry walk at all seasons ; and, where the soil contains a consid- 
erable quantity of stones, which have been thrown out in the 
process of trenching, or the rubbish of building-materials, this 
affords a good medium of getting them out of the way. 

On dry, gravelly ground, however, these excavations are use- 
less, so far as drainage is concerned ; and, shovelling aside the 
mere surface-soil, the walk may be laid down on the substratum 
beneath it. If the walks are on a level, or nearly so, the water 
generally finds its way off as quickly as it falls, and the cost of 
excavation is saved. 

The surface of walks may be formed of grass, gravel, or sand. 
Good gravel is the best, sand the very worst, and grass can only 
be introduced with propriety in particular places. Sand, or 
loose gravel, makes a very uncomfortable walk, and, when of 
great length, is tiresome and disagreeable to walk upon. 

A very common error, among those not acquainted with the 
proper method of making walks, is, to lay on too much surface- 
material; and, in many places, we have seen trenches taken 
out for walks, and filled, to the depth of a foot or more, with 
gravel, which, if laid on a hard surface to the depth of an inch 
or less, would have made a good walk, but which, at such a 
depth, all the walking, rolling, and pressing of years could never 
make it bind. It requires more skill than is generally supposed 
to make good walks. Among all the operations of the garden- 
maker there is scarcely one which we are so much disposed to 
find fault with, as in the making of walks ; and this is precisely 



118 FORMATION OF GARDENS. 

our reason for adverting to a matter which is apparently irrele- 
vant to the general character of the present work. 

The durability and comfort of walks consist chiefly in their 
power of resisting the action of the feet in walking on them, at 
all seasons of the year. Soft gravel walks, that yield no resist- 
ance to the motion of the body, are obviously unfit for being in 
a place where frequent walking is resorted to. Sand, also, 
makes a pretty walk to look at, but should never be employed 
where a good hard walk is required, unless it naturally pos- 
sesses the property of binding. 

It is quite possible, however, to have a hard solid walk, capa- 
ble of resisting the action of the feet, and yet appear to have a 
gravelly or sandy surface, which is frequently admired. This 
is effected by preparing the lower strata of open material, then 
a substratum of binding material, and lastly, a thin layer of 
whatever material is wished for the surface, which should be 
sifted before being laid on. It is then well watered, if dry; 
then rolled well in, which has the effect of mixing it with the 
binding stratum beneath, and leaving a smooth surface, that 
becomes harder the longer it is used. In making up the sub- 
strata, it is necessary to tread each layer firmly as it is made 
up, so that no hollows or inequalities may occur on its subsida- 
tion, and subsequent use. 

It must be remembered that the material of which the surface 
of a walk is composed, will not bind by any mechanical means, 
unless it contains something of a binding nature within itself. 
Clean gravel will not bind by any degree of mechanical pres- 
sure, unless it contains something to induce a general compact- 
ness and solidity over the whole surface. 

The best material which we have met with in this country, 
and which is no doubt abundant in many places, is a kind of 
soft decomposing sandstone rock, containing a large quantity of 
oxide of iron. It must be laid down where it is finally to 
remain, when newly taken out of the pit, then subjected to a 
good shower of rain, or watered, and afterwards rolled or well 
trodden with the feet ; it makes a solid walk, nearly as compact 
as the rock itself. It may be objectionable on account of its 



FOE a .'JEM. 

. . . .'-•>-'■ 
..■■...•.•• 

. ' . ■ ' . . 

*".o: ...-:*- .."'</.^ v.- . '. •■'.-;'. ::..-.._''.-.•:••:: ■ . .;. -.--> y^ - : 

-....■■.■.■. ^aUk. 
- 

•• - - - -' : - • '.'. .>•;•:• 

'- -. . 

"'.-'-. ■-.■/-■--■-.. ; ■•-.;;-: : .-. .-.- %.! . •. Lfc* & ;-;^: ■.-..■_ -'. ■_•■.- 

- . . 

an: sr-p-: . •-. ;• : ...« -..;• ; : :'.-. . .-. 

. ..... 

*■:'.:.'. ;,•'..-. -.. '.•....-;. -.-. •..'.. ■-.'--.- :'..:■■-.: /.;■,/;■ Ti ak 
... -. . 

.-..':. •■-..•-..: 

'!--•: : -."-. -.:' \-.-: \. :■'..-, .-,',. ; V: • % • V ;•-: . > - . 

.-...;..-'-:. . 

... . . . -. 

.... 

: • . . . ....-.-.-.■ 

\ - . . . _ . 

... 
. . ' : . 

*.v:i*rr_ : ■ ■■.■-'. ■/-. ;■ .\ --.-.■.■. \\-. ■ . :'■'.■ %.'.: . . ; - : ?'^ .-..' 
'X:..y -. . ■•: -.■:.;■. :'-.: :%;■*.:, '.:' ■-.:;-• v v.- '/:•. \-.- : ■ * - ;•:'- 

cTc. -..',': 1 r: ••-. ■: "': •: ' ;; "r . -.'V.-.'--: \ v ' ': ' '.' '. .' > ! 

:...'.■ ■•-- ' •.=: '- . : '.«- ' c :■: . - .': .: ' ": ' , : - \ \ H\ V. *..C\ 

^:^:. v.-. - v.»: ': '.i >•■: ."'.•-.: . . > . •: .- -. - v.\.v ;--:•;■:'.. 

:j*i and hOerwr Cs/mpxrtYMmtt. — The wi<|& «f g*e 

'sr'.^-.-; -..z% -.: - - '."^ v.-. - -: o- : '.;;, >-^: . ; - - 

.-^ .;-".: v ::.- ■■■-. :■,■/, \ ■ '. '-.■-.■-.:. :-:\ :' v.--. r- -'-■ '+"-- 
11 



120 FORMATION OF GARDENS. 

best general rule that can be laid down is to make the breadth 
of the borders equal to the height of the wall or boundary fence, 
whatever it may be ; they may be made broader, but not nar- 
rower, for then they produce a bad effect; a narrow border 
beside a high fence is very displeasing to the eye. 

The size and number of the compartments are determined by 
the number and disposition of the walks. It is decidedly a bad 
plan to have too many walks, as the ground is not only taken 
up with them, which require a deal of labor to keep them clean, 
but the effect of the garden is lessened. If less than two acres 
be enclosed, a walk running parallel with the boundary, say 
twelve feet distant from it, and another intersecting the garden 
in the middle, running south and north, will be sufficient; if 
more than two acres be enclosed, another intersecting walk, run- 
ning east and west, may be introduced. If the garden be 
worked by horse labor, the larger the compartments the better ; 
if wrought entirely by manual labor, these compartments may 
be sub-divided for the crops, by rows of fruit-trees, or fruit- 
bushes, as may be required. It should be observed, that to 
have a few walks, and those of good width, gives the garden a 
better appearance, and is in every way preferable to having a 
large number of contracted ones, and it leaves the compartments 
to be sub-divided by alleys or other means, as may be most con- 
venient for access to the crops. 

In many gardens, trellises or espalier rails are adopted. The 
proper place for an espalier rail trellis is on the inside of the 
principal walks, leaving a border of at least six feet. Many 
gardeners condemn them, and perhaps justly, in small gardens, 
as it confines the ground too much ; but in large gardens, espa- 
liers, if well managed, are both useful and ornamental. The 
railing should be plain and neat, not more than five or six feet 
high, with the upright rails, to which the trees are tied, about 
eight inches apart. 

It is not our purpose, at present, to dwell on the laying out 
of gardens. We have merely adverted to the subject, in so far 
as it is connected with the object of this treatise. 



FORMATION OF GARDENS. 121 

Walls. — As garden walls may be regarded as horticultural 
structures, we will here make a few remarks upon them. 

In Europe, walls are built around gardens of all kinds, 
whether the enclosed space be one or twenty acres. Their 
chief use is for training the more tender kinds of fruit-trees 
upon their southern aspect. The enclosed space is generally 
appropriated to the growth of culinary vegetables, and contain- 
ing also the hot-houses, which occupy a part of their south 
aspect. These gardens are of various forms, and we have seen 
them circular, oval, square, and oblong. The latter shape, with 
the angular corners cut off, is undoubtedly the most desirable 
shape for a vegetable garden. The oval and polygonal forms 
are preferred by some, on account of their affording a more equal 
distribution of sun and shade. But we are at a loss to find out 
how this can be the case, as, however a wall may be placed, 
it can only obtain a certain amount of direct sunshine during 
the day, and the inconvenience resulting from the adoption of 
these forms is very considerable, both in the management and 
culture of the interior compartments, and in the training of the 
trees. Moreover, an equal distribution of sunshine is not so 
desirable as may appear; as, while the warmest portion of the 
wall may be appropriated to the more delicate and early fruits, 
the coldest, or northern portion, may be as profitably appropri- 
ated to late sorts, or for retarding earlier kinds, both of which 
purposes are as useful as an early aspect. 

In this country, walls have been little employed in the forma- 
tion of gardens, and only in a few places have they been 
adopted, as at the fine gardens of Mr. Cashing, at Watertown, 
and Col. Perkins, at Brookline, in the vicinity of Boston, — two 
of the finest gardens in this country. Some other places have 
also portions of walls surrounding the garden, but we have seen 
none where any principles of design have been adopted and car- 
ried out so much as at the former placed 

* In Hovey's Magazine of Horticulture, pp. 50 — 53, vol. xvi., we 
have described the beautiful gardens at this place, from a visit which 
we gave them at that time. We have subsequently visited them, as 
well as many other places, and still consider them the finest gardens we 
have seen in America. They are made precisely in the style of modern 



122 



FORMATION OF GARDENS. 



In nearly all gardens, trellises and wood fences are employed 
instead of walls, as enclosures to the garden ground ; and these 
are well adapted for the purpose, as the fruits which require 
the protection of walls in England thrive and produce their 
fruit in greater perfection as open standards here. The utility 
of walls, however, around a garden, cannot be doubted, even in 
this country, especially as regards the protection they afford to 
trees trained on them, in early spring. Walls may be consid- 
ered as useful to plants trained on them, or near to them, in 
three ways: — first, by the mechanical shelter they afford 
against cold winds ; secondly, by giving out the heat they had 
acquired during the day; and, thirdly, by preventing the loss of 
heat which the trees would sustain by radiation. [See Experi- 
ments by Dr. Wells, in the third part of this work, Section VI. 
Protection of Plant-houses during Night.'] 

The same arguments which have been applied in favor of 
the best aspect for hot-houses, [see Section I.,] are equally appli- 
cable to walls. In the middle and southern states, we should 
think walls having a due southern aspect decidedly objectiona- 
ble, and, for tender and delicate kinds of fruit-trees, would decid- 
edly prefer either a south-eastern or a south-western aspect. 

The height of walls, or fences of any kind, round a garden, 
should always correspond to the space inclosed. Twelve feet 
may be taken as a maximum height. In England, low walls 
produce a greater effect in accelerating fruit than high ones ; 

English gardens, surrounded with fine walls, with the principal range 
of hot-houses, about 300 feet in length, on the southern aspect of the 
wall on the north side of the garden, and a smaller range on the inside 
of the east and west walls, all lean-to houses. There are convenient 
back-sheds and other offices on the north side of the hot-houses. There 
is no wall on the south side of this garden, which we think is very 
appropriately dispensed with. We regard this as a general rule, and 
more especially in gardens of small size, as it gives the enclosed spaces 
a less meagre and confined appearance. This garden, alone, of any 
which we have seen in this country, bears an impress of the style and 
genius of Loudon. And though we have some faults to find with the 
surrounding grounds, nevertheless, we believe, taking it all in all, it is 
the most perfect specimen of modern European gardening in this coun- 
try. 



FORMATION OF GARDENS. 



123 



but in this country the great radiation of heat from the earth, 
during the heat of summer, would render low walls of little use. 
On the other hand, high walls have always a gloomy effect, and, 
where it is necessary to have high walls round a garden, it is 
better to relieve the monotony of the wall by making it of differ- 
ent heights. 

Hot, or flued, walls are very common in European gardens, 
and have been used upwards of a century; and, in our opinion, 
where walls can be of any importance in this country, in the 
practice of horticulture, it must be chiefly as flued walls. In 
summer, the protection of a wall is not required to ripen the 
common fruits, and in hot summers they are frequently injuri- 
ous, by the attraction and radiation of heat during the midday 
sun, by which the leaves are sometimes scorched. It must be 
as protectors of peach and apricot blossoms in spring, and accel- 
erating the ripening of grapes in autumn, in which they can be 
most serviceable to the horticulturist ; and for these purposes hot 
walls are of great benefit. [See Wall Heating, Part II., Sec. V.] 

Flued walls can be built as cheap, if not cheaper, than solid 
ones, and are invariably built of brick; indeed, a considerable 
saving of material is effected, as little more than half of the 
bricks required to build a solid wall will build a hollow or flued 
wall ; and, unless a flued wall be desired, it is better to dispense 
with a wall altogether, for although a wooden paling will not ab- 
sorb so much heat as a brick wall, as a structure for mechanical 
shelter it is in every way equal to it, providing it be boarded 
perfectly close, and sufficiently high. The comparative cheap- 
ness of wooden fences, for gardens, must give them the prefer- 
ence, and the comparative beauty of brick walls and wood 
palings is a matter of taste which must be decided by the pro- 
prietor. 

Walls, or close palings, must, in all cases, be faced with a 
light trellis, made of laths or wire, to which the trees can be 
trained. The injury resulting to trees nailed on walls, in our 
gardens, is owing to their touching the material of the wall. 
The branches should be trained at least six or eight inches from 
the surface, so as to admit a stratum of air between the wall 
11* 



124 FORMATION OF GARDENS. 

and the branches. When this is attended to, no injury results 
to the foliage, even in the hottest of seasons. 

Boarded walls have long been used in northern countries, and 
are frequently made to incline considerably towards the north, 
so as to present a better angle to the sun's rays than if standing 
upright ; an expedient which here is unnecessary. 

We cannot help thinking that flued walls are worthy of more 
attention from horticulturists than they seem to have had, espe- 
cially when early fruit is desired, without the trouble and expense 
of a glazed structure, as an expedient for a hot-house. [See cut 
50, in the next part of this work, page 245.] 



PART II. HEATING 



SECTION I. 

PRINCIPLES OF COMBUSTION. 

1. To warm hot-houses, etc., most economically and efficiently, 
we must study not only the principles of heating, but, also, 
the principles of combustion. And as we are yet far from 
having obtained a complete knowledge of the most profitable 
manner of submitting coal and other kinds of fuel to the process 
of combustion, or, of applying the caloric so obtained to increase 
the temperature of hot-houses, it will, therefore, be desirable to 
begin at the beginning of this part of our work, and before treat- 
ing on the different mechanical contrivances in common use for 
the generation and diffusion of heat by combustion, let us first 
consider the principles upon which these ends are to be obtained. 

The subject before us involves a consideration of the nature 
and properties of the various kinds of fuel. It examines the 
chemical action of their several constituents on each other. It 
applies those inquiries to the class of chemical results which 
may be useful, and avoids those which are injurious. It involves 
also, in an especial degree, the closest observation on the sepa- 
rate influences which each of the constituents of atmospheric 
air exercises on combustible bodies, in the generation of those 
extra ordinary elements of nature, heat and light. And, finally, 
it investigates the cause and character of flame and smoke, and 
the influence these have on the former. 

Economy of fuel being one of the most important points to be 
sought for in a heating apparatus, we must inquire whether our 
common furnaces be so constructed as to give us the maximum 
quantity of caloric, for the fuel that is consumed. "We, there- 



126 HEATING. 

fore, must look into the furnace, and consider chemically as well 
as practically, the operations which are there going on, so that 
we may improve its arrangements, and adapt them so as to give 
full practical effect to the several processes which constitute 
combustion. 

To enable our practical readers to obtain a more accurate 
knowledge of the processes going on in the furnace, and of the 
results of the common mode of managing the fires of extensive 
forcing houses, we will enter more fully upon the constituents 
of coal, and the gases thereby generated, which form such an 
important part of the fuel itself, and which, by their escape into 
the atmosphere from the chimney, or into the atmosphere of the 
house from the flue, become the source of immense loss of heat. 
And, in the latter case, the loss is more than doubled, as they 
are destructive in the highest degree to every kind of vegetable 
life. 

In undertaking to show how these evils may be remedied, we 
must not be understood to concur in the exploded opinion, that 
these gases may be consumed by the methods hitherto used for 
that purpose, viz., by passing the smoke over a body of red-hot 
fuel at a distance from the burning and smoking mass. And 
however desirable it may be to know of some way of preventing 
smoke from being emitted in clouds from the chimney of hot- 
houses, yet, if we can discover no other method of obviating the 
evil, except " burning it," according to the common acceptation 
of that word, I fear we must continue to put up with the loss 
and annoyance as it is. 

It is not our purpose here to show how the smoke from fuel 
may be burned : but rather, we will attempt to show how fuel 
may be burned without smoke. And, let it be observed, this 
distinction involves the main question of economy of fuel. 

When smoke is once produced in a furnace or flue, we believe 
it to be as difficult to burn it, (and convert it to heating pur- 
poses,) as to burn and convert the smoke issuing from the flame 
of a candle to the purposes of light. If, indeed, we could collect 
the smoke and unconsumed gases of a furnace, and separate 
them from the products of combustion which the flues carry off, 
they might, subsequently, be made instrumental to the purposes 



PRINCIPLES OF COMBUSTION. 127 

of heat ; but, by the common method of constructing furnaces, 
their collection is impossible. 

When we see smoke issuing from the flame of an ill-adjusted 
common lamp, the heat and light are diminished in quantity. Do 
we attempt to burn that smoke ? No ; it would be impossible. 
Again, when we see a well-adjusted lamp burn without pro- 
ducing any smoke, the flame is clear and white. But here, the 
lamp has not burned its smoke ; it has burned without smoke; 
and it remains to be shown why the same methods may not be 
employed with regard to common furnaces, whereby they may 
burn without smoke, and thereby give out a greater quantity of 
heat, as in the case of the common and Argand lamp, since the 
elements of combustion in both cases are the same. 

2. In pointing out the leading characteristics in the use of 
coals, it is unnecessary to enter into detail of the various pro- 
cesses of gasefaction. We will, however, give this part of our 
subject a little attention, as the greater portion of the practicable 
economy in the use of coal, and the management of furnaces, 
will be found more or less connected with the combustion of the 
gases which arise from the combustion of fuel, and as the numer- 
ous combinations of which they are susceptible embrace the 
whole range of temperature, from that of flame down to the 
refrigeratory point. 

The subject of gaseous combinations, then, is undoubtedly an 
important part of our inquiry. And those who would study the 
economy of fuel, and the obtaining from it the greatest quantity 
of heat, cannot altogether dispense w T ith the part of our subject 
which at present lies before us. Though it may not appear 
equally interesting and important to every one, it is, neverthe- 
less, the alpha and omega of the whole process of combustion. 
The gardener may say, what has this to do with gardening? 
But we tell him, plainly, that this is an essential part of his 
business, which will be generally admitted by intelligent men, 
that so long as a furnace is connected with a hot-house, and 
fuel consumed in that furnace, this must necessarily be a part 
of his business. 

On the application of heat to bituminous coal, the first result 



128 HEATING. 

is its absorption by the coal, and the consequent disengagement 
of gas, from which all that subsequently bears the character of 
flame is exclusively derivable. This gas, whether it be in a 
close retort, or in a furnace, is associated with several other 
substances, more or less tending to deteriorate its inflammable 
properties and powers of giving out heat and light. In the 
preparation of gas, or smoke, for illuminating purposes, these 
impurities are separated, and the pure gas alone is used. As, 
however, this separation cannot be effected in a common furnace, 
and, as the entire gaseous products of the coal, good and 
bad, are indiscriminately consumed together as they are gener- 
ated, it is the more incumbent on us to be cautious, lest, by any 
injudicious arrangement, we force these impurities into more 
active energy, and thus increase their deleterious power. 

We will not stop here to consider the nature of those impuri- 
ties arising out of the unions of sulphur, and the other injurious 
constituents of coal, although they exercise a mischievous in- 
fluence on the calorific effect of the gas burning in the furnace, 
but will consider those constituents alone, which unite in form- 
ing the useful gases, and from which we are to derive heat. 

These constituents are the hydrogen and the carbon. And 
the unions which alone concern us here, are, first, carburetted 
hydrogen; and, second, bi-carburetted hydrogen, commonly 
called defiant gas. These two, and their unions with the air, 
in the process of combustion, we will shortly examine. 

Gases, as well as other bodies, endowed with the power of 
giving out heat and light, have been called combustible. This 
term has been a source of much error in practice, from a mis- 
conception of its meaning, under the received impression that 
combustibles possess, in some undefined manner, and within 
themselves, the faculty of burning. And, though every person 
knows that they will not burn without air, still the part which 
air acts in the process is but little inquired into. It is but lately 
that the nature of this union of the gas with the air has come to 
be fully understood ; and, although the abstract question as re- 
gards the immediate cause of that chemical action, which we 
k ?all combustion, may continue to be disputed, and new theories 
continue to be broached, still, for all practical purposes, it is 
sufficient! j denned and understood. 



::z 1:7775 7 111777::: 199 

And here we are called no. to in dre n :th reference to the 
girrr under consideration, wneniT :ir:r are e.it lecnliar 
conditions which can influence the :: : heal i be : 

tuned from them? and, if so, what they are ? This, again 
es other questions in referem i rar and 777 part which. 
umuLiii and thns we find omselres intro- 
duced into the chemistry of c: 

'. Q€ advantage :•: receiving tie subnect ii this lighl . land 
ill see how idle would be ::." :: . i. . : d : bb : r arj angiiia eafe 

- 1.111 :: : ; : i 77 i e: : i "7 7: : ~ ei 

erainined and under- : : the rafjunale vhieh 

m ie777i mi 17 1 111 :■= : : 711.7 7: .- 7:: wis.i :ienir; 
w:n begin 77 ieii ; : : : . n : .1:111 :i : : hi :i:~ 1:17: 
77777:11 hi 77 :_: : :::. in: the .::-.:-; ':.: pTirp^es i 

-_ _t It :>7 ::: .-.: V i... ::i every-*lay 

nine :: i:i~_: :::n _ : 111:1 :.: in ;_iir usurers 
7it ibsurdity ■::" iks> 777111 and one 711771 ban arfakli it 
lands nracfacai men, will be more apparei: —7.77. —7 ime to 
7:1s: ier 71 e n 7717 :: '7-1 . _ . - ■ 771 lie p:~ e: 

lien: —71:1 -11 1 nil 

.": : "" - ";:: 7171 11 : 11:7-- 1 717 11:17711 7ikei 
77 1 is 777:71' 7 1:1" "i__:_ 11 7 briTiri" - :: 
7:1:1 1.1 :_i_ :77 .1 11: 117:1: '..— 1 7 111:77:17 1:7.1-17 
sit lie: :•::." I: 1 1 11 : :i 1: — 171 1 171111 
It 111117 —11 1 _ : win 1: ■ :i 7: 

:i-.-: 1- : rrc"7f* ZS enez 1 ~:ii i:~7-i: 11 :n 
717 7 11 It 1 11117 : 

I: t!7! ill:. 11: "i :ii- 1: -7 : 11:1111 2.7: 
: 1 :re: 1 1111 7.11 77:111 111:1:1 

1711 : .1: ::: 1 111 171:7. 11 1 — 1 7 1 17 ::■ 

: 1177 7117771 7 717 7H 1 1 _1" 

11 . __- — _.i 17 .in :•;' heal i :: i" i is -.111: 
g :_ti::i 1: : 1 1 11 1: 1 1 1 1: 1: 

- 1 111 1 : .1 1 771 ;i 7 7- 1 1 . 1 - 7 :77.i 1 1 : 1 

1717-77.77 17 1 It - 1.11.7 117. .1 .7.1 1717 111- 

: 1 717 : 1. 1. : 11 1 1.11 
:: It 71 1 1- 1 - ..-..- - - t - 



130 HEATING. 

that exactly in the ratio that such union is complete, is the quan- 
tity of heat increased. 

But we have not the means of obtaining this necessary sup- 
porter in sufficient quantity, in a separate state, except at an ex- 
pense which would render it incompatible with the purposes of 
a furnace. Our only alternative then is to apply to the atmos- 
phere, of which it forms a part, in order to satisfy our wants. 
Had we to purchase this oxygen, we would, necessarily, be more 
economical of its use, and inquire more respecting its application. 
But, finding an abundant supply at hand, in the atmosphere, 
and obtaining it without expense, we are careless of its use, and 
unconscious of its value, and take no note of the large 
quantity of the noxious ingredients with which it is accompanied, 
or loss sustained, by diminishing the supply; and hence, many 
of the evils, such as bad apparatus, bad fuel, and bad furnaces, 
might be easily remedied, were the properties of these gases fully 
understood. 

The unions we have now to consider are those which take 
place between the constituents of the coal and the atmospheric 
air, namely, the hydrogen and carbon of the former, and the 
oxygen of the latter. Dr. Ure calls the carbonaceous part of 
coal, " the main heat-giving constituent." In this he must be 
understood to include that portion of the carbon which forms 
one of the constituents of the gases alluded to, and, although, 
for the purposes of the furnace, so much value is set upon the 
solid part — the coke — we must not, on that account, undervalue 
the heat-giving properties of the gas. Indeed, the extent of 
those powers is strikingly brought before us, by the fact, that for 
every ton of bituminous coal no less than 10,000 cubic feet of 
gas are obtained. 

When we consider the immense heating powers of such a 
mass of flame as would be produced by 10,000 feet of gas, we 
cannot resist the conclusion, that there must be something es- 
sentially wrong in the mode of bringing it into action within a 
furnace, as compared to its well known efficacy in an argand 
burner. That this is the fact, will appear manifest as we pro- 
ceed. And one of our objects is to show how greater heat may 
be obtained by the combustion of the volatile products of the 



PRINCIPLES OF COMBUSTION. 131 

coal, than by allowing the whole body of gas to escape into the 
atmosphere. 

Let us bear in mind, that smoke is always the same, whether 
it may be generated in a common fire-place, in a furnace, or in a 
retort ; and that, strictly speaking, it is not inflammable, as by 
itself it can neither produce flame nor permit the continuance 
of flame in other bodies, as is proved from the fact that a lighted 
taper being introduced into a jar of coal gas, (or smoke,) is 
instantly extinguished. 

How, then, is it to be consumed or prevented, and rendered 
available for the production of heat ? The answer is, solely by 
effecting a chemical union, not with the air merely, as is the 
dangerous notion, but with the oxygen of the air, — the "sup- 
porter" of flame, the heat-giving constituent of the air, in given 
quantities, and at a given temperature. 

This at once opens the main question, What are these quan- 
tities, and what is this temperature ? and, are there any other 
conditions requisite for effecting the chemical union of the 
oxygen of the air with the inflammable gas, to the best 
advantage ? 

Effective combustion, for practical purposes, is, in truth, a 
question more as regards the air and the gas ; and the former, 
as referable to our object, would appear better entitled to the 
term combustible than the latter, inasmuch as the heat is in- 
creased in proportion to the quantity of air we are enabled to 
use advantageously. Besides that, we have no control over the 
gas after having thrown the fuel on the furnace, but we can 
exercise a control over the air, as we shall show, in all the 
essentials of perfect combustion. It is this which has done so 
much for the perfection of the lamp, and may be rendered 
equally available for the furnace. 

Now, although this control, and the management arising out 
of it, influences the question of perfect or imperfect combustion, 
and, therefore, affects that of economy, yet, strange to say, in an 
age when chemical science is so advanced, and in a matter so 
purely chemical, this is precisely what is attended to in practice. 
The how, the when, and the where, this controlling influence 
over the admission and the action of the air is to be exercised, 
12 



132 HEATING. 

are points demanding the most attentive consideration from all 
who are interested in these matters. 

Much confusion at present prevails in all that regards hot- 
house furnaces, as well in their practical working as regards the 
admission of air and the combustion of fuel. In commenting 
briefly upon the constituents of coal smoke, or coal gas, car- 
buretted hydrogen, and the quantity of air required for their 
combustion, we will be as explicit as possible, without going 
more into scientific detail than is consistent with the means and 
opportunities of that class of practical men for whom we write. 

3. The first step towards effecting the perfect combustion of any 
combustible gas, is the ascertaining the quantity of oxygen with 
which it will chemically combine, and the quantity of air re- 
quired for supplying such quantity of oxygen. Here, then, we 
are called on for strict chemical proofs — these several quantities 
depending, not on the dictum of any chemist, but on the faculty 
which each particular gas possesses of combining with certain 
definite proportions of the other — the supporter ; these respec- 
tive proportions being termed " equivalents,'" or combining vol- 
umes. This doctrine of equivalents must, therefore, be under- 
stood before we can be prepared to admit the necessity of any 
precise quantities. This question, as to quantity, is also the 
more important when we consider that the quantity of effective 
heat obtained by the combustion of any body, will be in exact 
relation to the quantity of oxygen with which it will chemically 
combine. 

Let us begin, then, by inquiring into the constitution of the 
coal gas, and the relative proportions in which its constituent 
elements are combined, as these necessarily govern the propor- 
tions in which it will combine with the oxygen of the air. 

Now, the doctrine of " equivalents," that all-convincing proof 
of the truths of chemistry, being clearly defined and understood, 
reduces, to a mere matter of calculation, that which would 
otherwise be a complicated tissue of uncertainties. And let no 
mechanic feel alarmed at this introduction to " elementary atoms " 
and " chemical equivalents," or imagine it will demand a deeper 
knowledge of chemistry than is compatible with his sources of 



PRINCIPLES OF COMBUSTION. 133 

information; neither let him suppose he can dispense with the 
knowledge of this branch of the subject, if he has anything to 
do with the combustion of coal. Without it, he is at the mercy 
of every speculative "smoke-burning" pretender; whereas, 
with it, his mind will be at once opened to the simplicity and 
efficiency — I may add, to the truth and beauty, of nature's 
processes, as regard combustion. 

There is not, indeed, a more curious or instructive part of the 
inquiry than that respecting the conditions and proportions in 
which the compound gases enter into union with the constituents 
of the air ; neither is there one more intimately connected with 
the practical details of our furnaces. These introductory remarks 
are, therefore, necessary for those who are not already familiar 
with it. Indeed, without some information on this head, the 
unions of the gases might appear capricious or uncertain; 
whereas, in fact, they are regulated by the most exact laws, and 
subject to the most unerring calculations.^ 

* Mr. Parkes observes : — * We are unfurnished with any definite, 
determinate experiments regarding the proportions in which air and fad 
unite during combustion. "We are, practically speaking, altogether ig- 
norant of the mutual relations which subsist between the combustible and 
the supporter of combustion, (the fuel and the oxygen ;) and, though we 
know that, without oxygen, we cannot elicit heat from coal, we have ye: 
to discover the most productive combinations of the two elements. 

" Here, then, remains a wide field for research and experiment, wor- 
thy, and. indeed, requiring the labors of a profound chemist."' 

These matters are now better understood, and those " most productive 
combinati-ons" rendered familiar and certain, by the labors of that "-pro- 
found chemist/'' John Dalton, who first drew the attention of the chemical 
world to the subject of equivalent proportions, and taught us the impor- 
tance and necessity of ascertaining those proportions — in fact, of 
" reasoning by the aid of the bale 

Dalton" s papers were first read before the Manchester Philosophical 
Society, and published in their memoirs, in the year 1603. These vol- 
umes are very scarce, and I have not been able, anywhere, to meet with 
a complete copy of them. The P^oyal Institution, where Davy brought 
his great discoveries to light, contains but the five volumes of the first 
series. These volumes, or. at least, the papers of Dalton, should be re- 
published, for the purpose of showing the correct chain of reasoning 
by which the mind of that acute philosopher proceeded. 



134 HEATING. 

Much of the apparent complexity which exists on this head 
arises from the disproportion between the relative volumes, or 
bulk, of the constituent atoms of the several gases, as compared 
with their respective weights. 

For instance, an atom of hydrogen (meaning the smallest 
ultimate division into which it is supposed to be resolvable) is 
double the bulk of an atom of carbon vapor ; yet the latter is 
six times the weight of the former. 

Again, an atom of hydrogen is double the bulk of an atom of 
oxygen ; yet the latter is eight times the weight of the former. 

So of the constituents of atmospheric air, nitrogen and 
oxygen. An atom of the former is double the bulk of an atom 
of the latter ; yet, in weight, it is as fourteen to eight. 

A further source of apparent complexity arises from the 
faculty of condensation, or diminution of bulk, which, in certain 
cases, attends the union of the gases. For example, one volume 
of oxygen and two volumes of hydrogen, when united, condense 
into a volume equal to that of the hydrogen alone, (the weight 
being, of course, the sum of both;) that is to say, one cubic 
foot of oxygen chemically combined with two cubic feet of 
hydrogen condense into the bulk of two cubic feet : and so on, 
each union bearing its now ratio of volume and weight. This 
apparent complexity, however, we shall soon see give way to a 
systematic consideration of the subject. 

We have stated that there are two descriptions of hydro-carbon 
gases, in the combustion of which we are concerned; both being 
generated in the furnace, and even at the same time, namely, 
the carburetted and bi-carburetted hydrogen gases. For the 
sake of simplifying the explanation, I will confine myself to the 
first, as forming the largest proportion of the gas to be consumed, 
namely, the carburetted hydrogen, or common coal gas, as I shall 
call it for the sake of brevity. 

Now as, during combustion, the atoms of this gas become 
decomposed, and its constituents separated ; and as these will 
be found to exercise separate influences during the process, it is 
essential that we examine them as to their respective properties, 
weights, and volumes. 

On analyzing this mixed gas we find it to consist of two vol- 



PRINCIPLES OF COMBUSTION. 



135 



umes of hydrogen and one of carbon vapor; the gross bulk 
of these three being condensed into the bulk of a single atom of 
hydrogen ; that is, into two fifths of their previous bulk, as shown 
in the annexed figures. Let figure A represent an atom of coal 
gas — carburetted hydrogen — with its constituents, carbon and 
hydrogen ; the space enclosed by the lines representing the rela- 
tive size or volume of each ; and the numbers representing their 
respective weights — hydrogen being taken as unity both for vol- 
ume and weight.* 

Carburetted Hydrogen. Bi-carburetted Hydrogen. 



A. 



1 atom of 

the above gas. 

weight 8. 



its 

constituents, 



1 atom of 
Hydrogen, 
weight 1. 



1 atom of 
Hydrogen, 
weight 1. 



1 atom of 
Carbon, 6. 



1 atom of 

the above gas, 
weight 14. 



its 

constituents. 



1 atom of 
Hydrogen, 
weight 1. 



1 atom of 
Hydrogen, 
weight 1. 



1 atom of i 
Carbon, 6 



1 atom of 
Carbon. 6. 



* " Ce gaz (carburetted hydrogen) est compose de 75.17 parties (by 
weight) de carbone, et 24.33 d'hydrogene ; ou, d'un volume de carbone 
gazeux et quatre volumes de gaz hydrogene, condenses a la moitie due 
volume de ce dernier, ou, aux 2/5 du volume total du gaz, de maniere 
que de cinq volumes simples, il n'en resulte pas plus de deux de la com- 
binaison." — Berzelius, vol. i. ; p. 330. 



12* 



136 



HEATING. 

Or they may be represented thus 
Carburetted Hydrogen. 




its constituents, 




Bi-carburetted Hydrogen. 




its constituents, 




Although not intending to take any further notice, in this 
place, of the bi-carburetted hydrogen, I have, however, annexed 
the above diagrams, representing this gas and its constituents, 
that both may be under view at the same time ; and by which it 
will be seen, that although, in volume, the two gases are precisely 
the same, there is yet double the quantity of carbon in the bi-car- 
buretted that there is in the carburetted hydrogen : this circum- 
stance is of great importance, and must be kept in our recollec- 
tion, as these proportions will be found to have a considerable 
influence during the subsequent process of its combustion. * 

* The mode of representing the volumes of gas, by rectangular figures, 
as adopted by Mr. Brande and other chemists, is favorable, so far as 
single atoms are concerned, inasmuch as the eye at once recognizes the 



PRINCIPLES OF COMBUSTION. 137 

I would here observe on the importance of keeping in mind 
this double relation of weight and volume, and the atomic consti- 
tution of these gases, as it will prevent much of that confusion 
which too often embarrasses those who are not familiar with 
the subject of gaseous combinations. 

Let us now, in the same analytical manner, examine an atom 
of atmospheric air, the other ingredient in combustion. 

Atmospheric air is composed of two atoms of nitrogen and one 
atom of oxygen : and here again we find a great disproportion 
between the relative volumes of these constituents ; one atom of 
nitrogen being double the volume of an atom of oxygen, while 
their relative weights are as 14 to 8 : the gross volume of the 
nitrogen, in air, being thus four times that of the oxygen ; and 
in weight, as 28 to 8, as shown in the annexed figure. 



Atmospheric Air, (or thus,) Atmospheric Air. 



1 atom of 
Nitrogen, 
weight 14. 



1 atom of 
Nitrogen, 
weight 14. 



1 atom of 
Oxygen, 8. 









«-> 




< 




o 








o 




f.8 


equal 
to 


i 2 
2 & 




< £ 




v. £ 




o 




s 












eS 








Here we are relieved from the complexity arising out of any 
difference in volume between these constituents, when united and 
when separate. In the coal gas we found the constituents con- 
densed into two fifths of their gross bulk when separate : this, 
we see, is not the case with air ; an atom of which is the same, 
both as to bulk and weight, as the sum of its constituents. 



relation between volumes and half volumes. As, however, I shall have to 
do with masses of these gases, I have adopted circular figures, the rela- 
tion between the sizes of the volumes of the different gases being the 
same. 



138 HEATING. 

Thus, we find, the oxygen — the heat-giving constituent of 
the air — bears a proportion in volume to that of the nitrogen, as 
1 to 5 ; there being, in fact, but 20 per cent, of oxygen in atmos- 
pheric air, and no less than 80 per cent, of nitrogen ; a circum- 
stance which should never be lost sight of in all that has to do 
with its admission and application. 

Having shown the composition of coal gas, and also of air, 
with the weights and volumes of their respective constituents, 
we now proceed to the ascertaining the separate quantity of oxy- 
gen required by each of those constituents, so as to effect its per- 
fect combustion, and produce the largest quantity of available 
heat ; in other words, to find the " chemical equivalent" or vol- 
ume of air, required for the saturation of this mixed gas. 

Now, this is to be decided, not by the quantity of air we may 
admit or force into the furnace, but solely by the faculty with 
which each of these constituents is endowed of uniting chemically 
with the oxygen. 

With respect to this power, or faculty of reciprocal saturation, 
the first great natural law is, that bodies combine in certain fixed 
proportions only, — a remarkable feature in this law, as far as 
gaseous bodies are concerned, being, that it has reference both to 
volume and weight ; thus, by their concurrence, establishing the 
principle which now no longer admits of any doubt. * 

The important bearings of this great elementary principle of 
proportionate combination cannot be more strikingly illustrated, 
or its influence rendered more familiar, than in the several com- 

* " L'experience a demontre que, de meme que les elemens se com- 
binent dans des proportions fixes et multiples, relativement a leur poids, 
ils se combinent aussi, d'une maniere analogue, relativement a leur 
volume, lorsqu'ils sont a l'etat de gaz : en sorte qu'un volume d'un 
element se combine, ou, avec un volume egal au sien, ou avee 2, 3, 4 et 
plus de fois son volume d'un autre element a l'etat de gaz. En com- 
parant ensemble les phenomenes connus des combinaisons de substances 
gazeuses, nous decouvrons les memes lois des proportions fixes, que celles 
que vous venons de deduire de leurs proportions en poids ; ce qui donne 
lieu a une maniere de se representer les corps, qui doivent se combiner, 
sous des volumes relatifs a l'etat de gaz. Les degres de combinaisons 
sont absolument les memes, et ce qui dans l'une est nomme atome, est 
dans l'autre apelle volume." — Berzelius, vol. iv., p. 549. 



PRINCIPLES OF COMBUSTION. 



139 



binations of which the elements of atmospheric air are suscepti- 
ble, and the extraordinary changes of character and properties 
which accompany the changes, in the relative quantities alone, 
of the combining elements. 

For instance, oxygen unites chemically with nitrogen in five 
different proportions, forming five distinct bodies, each essentially 
different from the others, thus : 



Atoms. Weight. Atoms. Weight. Gross Weight. 

of Nitrogen 14 unites with 1 of Oxygen 8 forming Nitrous Oxide . . 22 



14 
14 
14 
14 



16 " Nitric Oxide . . 30 

24 " Hyponitrous Acid 38 

32 " Nitrous Acid . . 46 

40 " Nitric Acid ... 54 



Or thus : 




Atmospheric Air. 



Nitrous Oxide. 



Nitric Oxide. 



..Hyponitrous Acid. 



. m .......~~ Nitrous Acid. 



Nitric Acid. 



140 HEATING. 

A description of the properties of these distinct bodies may be 
found in any chemical work of authority, and I only mention 
these unions to exemplify the importance of attending to the 
proportions in which bodies unite ; as we here find the very ele- 
ments of the air we breathe, by a mere change in the proportions 
in which they are united, forming so many distinct substances, 
from the laughing gas, nitrous oxide, up to that most powerful 
and destructive agent, nitric acid, commonly called aqua-fortis. 

This case of the combination of nitrogen and oxygen also 
shows the importance of the distinction between mechanical and 
chemical union ; these two elements being only mechanically 
united in forming atmospheric air, by which the essential prop- 
erties of its two constituents as preserved unaltered ; whereas, 
in the five bodies above enumerated, the union is chemical, and, 
consequently, the essential characters of their respective con- 
stituents are lost, and new ones obtained. 

Now, to apply these principles to the bodies under considera- 
tion, namely, the carbon and hydrogen, and ascertain the propor- 
tions of oxygen they respectively require to produce chemical 
union. 

These two constituents, though united in the one body — the 
g as — . y e t, not only separate themselves during combustion in a 
remarkable manner, but, by two distinct processes, form two essen- 
tially different unions. This is an important feature of the 
development of chemical action which the law of equivalents at 
once points out and enables us to satisfy, although this double 
process does not appear to be understood, much less to be pro- 
vided for, in practice, though familiar to every chemist. 

On the first application of heat, or what may properly be 
termed the firing or lighting the gas, when duly mixed with air, 
the carbon separates itself from its fellow-constituent, the hydro- 
gen, and forms a union with the former, the produce of which 
is carbonic acid gas. 

Now, the laws of chemical proportion teach us that carbonic 
acid is composed of one atom of carbon vapor, (by weight 6,) 
and two atoms of oxygen, (by weight 16,) the latter, in volume, 
being double that of the former, as in the annexed figure : 



PRINCIPLES OF COMBUSTION. 141 



Carbonic acid. 




Thus, as far as the carbon is concerned, we obtain the infor- 
mation we sought, namely, its saturating equivalent of oxygen, 
and which we find to be just double its own volume; or, by 
weight, as 16 is to 6. But, without the aid of chemistry, we 
should here have remained satisfied ; combustion would appear 
to have been complete ; there would be no smoke, and no visi- 
ble indication of an imperfect or unfinished process. Yet, chem- 
istry tells us, we have only disposed of the one constituent of 
the gas, namely, the carbon, and that the hydrogen, the second 
constituent, remains yet to be accounted for, and converted to 
heating purposes. * 

It is true, the carbon was, in weight, equal to six parts out of 
eight (the original weight of the gas.) In bulk, however, it was 
but one fifth; and when it is recollected, that, although the 
illuminating properties of the carbon are superior to those of the 
hydrogen, yet that the heating properties of the hydrogen are 
far superior to those of the carbon, we can appreciate the loss sus- 
tained should these four fifths of the gas remain unconsumed. 

To this may be added, the probable injury done to the heat- 
ing powers of the flame by the conversion of any part of this 
otherwise valuable hydrogen into one of the most destructive 
compounds which can be met with in the furnace or flues, 

* I have here stated the case of the oxygen uniting with the carbon, 
before the hydrogen. Chemists are undecided on this point; and, indeed, 
the evidence at present is quite contradictory. 

It is to be observed, however, that the argument, drawn from the 
combustion of the carbon before the hydrogen, or vice versa, is the same, 
as regards the point now under consideration. "Whichever half passes 
off uncombined, is lost. 



142 HEATING. 

namely, ammonia, composed of unconsumed hydrogen and a 
portion of the nitrogen liberated from the air. Thus we have a 
double motive for providing against the escape, unconsumed, of 
the hydrogen of the gas. 

What, then, is to be done? Let us complete this second 
process as we did the first : let us supply this hydrogen, this 
remaining 80 per cent, in volume of the gas, with its own proper 
equivalent of oxygen, as we did in the case of the carbon. 

But what is this second equivalent ? By the same laws of 
definite proportions, we learn that the saturating equivalent of 
an atom, or any other given quantity of hydrogen, is, not double 
the volume, as in the case of the carbon, but one half its volume 
only — the product being aqueous vapor, that is, steam; the 
relative weights of the combining volumes being 1 of hydrogen 
to 8 of oxygen ; and the bulk, when combined, being two thirds 
of the bulk of both taken together, as shown in the annexed 
figure 8. P 

We thus find, that to saturate the one volume of carbon vapor, 
two volumes of oxygen are required ; whereas, to saturate the 
two volumes of hydrogen, one volume only of oxygen is required : 
thus, 

FIRST CONSTITUENT. 
Carbon. Oxygen. 

Vol. Atom. Weight. Vol. Atom. Weight. Vol. Atom. Weight. 

£ . . 1 . . .6 unite with 1 . . 2 . . .16 forming ) i i 2 2 

carbonic acid. J '"*."* 

SECOND CONSTITUENT. 
Hydrogen. Oxygen. 

Vol. Atom. Weight. Vol. Atom. Weight. Vol. Atom. Weight. 

2 . . 2 . . .2 unite with 1 . . 2 . . .16 forming j 2 2 18 



steam. 

Here we see, that, in the case of this first constituent, as 
above, the half volume of carbon and one volume of oxygen 

* Professor Brande puts this so clearly that I here give his own 
words : — " The simple ratio which the weights of the combining ele- 
ments bear to each other involves an equally simple law in respect to 
combining volumes, where substances either exist, or may be supposed 
to exist, in the state of gas or vapor. 

" Thus, water may be considered as a compound of 1 atom of hydro- 
gen and 1 atom of oxygen, the relative weights of which are to each 



PRINCIPLES OF COMBUSTION. 



143 



become condensed into one volume of carbonic acid (as shown in 
the last figure); and that, in the second constituent, the two vol- 
umes (meaning double bulk) of hydrogen, and one volume of 
oxygen, become condensed into two volumes of steam, (as 
shown in the annexed figure.) 

other as 1 to 8. Hence, the equivalent of the atom of water will be, 1 
hydrogen -f- 8 oxygen = 9. But oxygen and hydrogen exist in the gase- 
ous state, and the weight of equal volumes of those gases (or, in other 
words, their relative densities, or specific gravities) are to each other as 
1 to 16 ; hence, 1 volume of hydrogen is combined with ^ a volume of 
oxygen to form 1 volume of the vapor of water, or steam : for the specific 
gravity of steam, compared with hydrogen, is as 1 to 9. The annexed 
diagram, therefore, will represent the combining weights and volumes of 
the elements of water and of its vapor." 



Hydrogen, 1. 





Steam, 9. 


Oxygen, 8. 







Steam. 



or thus, 




The following is also much to the point : — "La composition de l'eau 
est un des elemens les plus necessaires aux calculs des chemistes, les 
derniers experiences de MM. Berzelius et Dulong out fourni pour sa 
composition des nombres qui sont adoptes T>ar f ous les chemistes. Elle 
est forme e d'apres eux de 

Oxygene 88.90 1 volume, oxygene. 

Hydrogene .... 11.10 2 volumes, hydrogene. 



100.00 



1 volume eau. 



Parmi les nombreuses decouvertes que la science doit a M. Gay Lussae, 
on remarquera toujours la belle observation sur la composition de l'eau, 
qui le conduisit a trouver les vrais rapports des gaz et des vapeurs dans 
leurs combinaison. Des experiences tres exactes, qu'il avoit faites con- 
jointement avec M. de Humboldt, lui prouverent que l'eau formee d'un 
volume oVoxygene et de deux volumes de hydrogene, resultat plainement 
continue depuis par tous les phenomenes ou l'eau joue un role actif, et 
qui s'accorde avec la composition trouve par MM. Berzelius et Dulong." 
— Dumas, vol. i. ; p. 33. 

13 



144 HEATING. 

No facts in chemistry, therefore, can be more decidedly 
proved, than that one atom of hydrogen and one atom of 
oxygen {the former being double the bulk of the latter) unite in 
the formation of water ; and, further, that one atom of carbon 
vapor and two atoms of oxygen {the latter being double the bulk 
of the former) unite in the formation of carbonic acid gas. 

Thus, the ultimate fact of which we were in search is, that 
the one condensed volume of the gas, as generated from the 
coal, requires two volumes, or double its bulk of oxygen, that 
being the quantity required for the saturation of its constituents 
ivhen separated. 

Now, this is the entire alphabet of the combustion of the car- 
buretted hydrogen gas. 

Having thus ascertained the quantity of oxygen required for 
the saturation and combustion of the two constituents of coal 
gas, the only remaining point to be decided is, the quantity of 
air that will be required to supply this quantity of oxygen. 

This is easily ascertained, seeing that we know precisely the 
proportion which oxygen bears, in volume, to that of the air. 
For, as the oxygen is but one-fifth of the bulk of the air, five 
volumes of the latter will necessarily be required to produce one 
of the former ; and, as we want tivo volumes of oxygen for each 
volume of the coal gas, it follows, that to obtain those two vol- 
umes, we must provide ten volumes of air. 

Thus, then, by strict chemical proof, we have obtained these 
facts : — First, that each volume of coal gas requires two vol- 
umes of oxygen ; secondly, that to obtain these two volumes of 
oxygen we must employ eight atoms of air ; thirdly, that these 
eight atoms of air are equal to ten volumes of the coal gas ; 
each volume of the latter, in fact, requiring ten volumes, or ten 
times its bulk of air : thus, 

Ten volumes of air are the same as eight atoms ; 

Eight atoms of air produce four atoms of oxygen ; 

Four atoms of oxygen are equal to two volumes of the same ; and 

Two volumes of oxygen saturate one volume of the coal gas : 

Therefore, ten volumes of air are required for each one volume of this gas. 

We now see why ten volumes of air are required for each 



PRINCIPLES OF COMBUSTION. 145 

volume of gas, and why neither more nor less will satisfy the 
conditions of its combustion. For, if more, the excess, inde- 
pendently of the mischievous chemical unions that might enter 
into it in the furnace, would be the means of carrying away as 
much heat as it would take up by its expanding faculty. And 
if less, a corresponding quantity of either hydrogen or carbon 
would be deficient of its supporter, and necessarily pass off 
uncombined and unconsumed. 

The only observation here necessary to make on the difference 
between these two gases is, that as this latter gas contains two 
atoms of carbon instead of one, it follows that a proportionate 
additional quantity of oxygen will be required for this additional 
atom of carbon. Hence, if carburetted hydrogen requires two 
volumes of oxygen for combustion, the bi-carburetted hydrogen 
will require three volumes. And so of air : if ten volumes of 
air are required for the one gas, fifteen volumes are consequently 
required for the other gas. 

4. We have seen that, in the formation of the carburetted 
hydrogen, a considerable portion of the carbonaceous constituent 
of fuel is separated, and carried away by the hydrogen in the 
gaseous form, forming the carburetted hydrogen ; the remainder 
of such carbonaceous matter is what we have now to deal with ; 
the difference as regards combustion between these two portions 
of carbon being so important as to demand especial notice. 

In observing this curious arrangement by which the saturation 
of the combustible atoms is effected, we perceive that three atoms 
of the combustible are apportioned to four of the supporter. 
This, we see, is the result of one atom of carbon requiring two 
of the supporters, while the two of hydrogen are satisfied with 
one each. 

Now, in this arrangement no excess or deficiency appears 
among the heat-producing ingredients. Could we have dis- 
pensed with or avoided the presence of such an excess of nitro- 
gen, (which is neither a combustible nor supporter of combus- 
tion,) the several unions would have been less embarrassed, — 
their combustion more rapid and complete, — and the intensity 
of their action much increased. That, however, was impossible. 



146 HEATING. 

The presence of so large a quantity of nitrogen being the una- 
voidable condition of obtaining the oxygen through the instru- 
mentality of atmospheric air, 

It is to be observed that the process of combustion here 
described is the most perfect that could be produced, either in a 
furnace or lamp. Any deviation, therefore, by means of excess 
or deficiency, or from any interruption or interference, such as 
the interposition of another gas, must be more or less destructive 
to the desired effect, viz. , the generation of the greatest quantity 
of available heat. 

5. When we speak of mixing a given quantity of oxygen 
with a given volume of smoke, (or coal gas,) we do so because 
we know that such quantity of the former is required to saturate 
the latter, and by such saturation every atom of both gases 
enters into union, without excess or deficiency of either, pro- 
ducing entire and complete combustion. 

So, when we speak of mixing a given volume of atmospheric 
air with a given volume of smoke, we do so for the same pur- 
pose, knowing that the precise quantity of air will provide the 
required quantity of oxygen. 

Thus, if we know that two cubic feet of oxygen are the exact 
saturating equivalent, or combining volume, for effecting the en- 
tire combustion of one cubic foot of coal gas, we know that ten 
cubic feet of atmospheric air will effect the same purpose, 
because ten cubic feet of air contain the required two cubic feet 
of oxygen. 

We require ten cubic feet of air to supply two cubic feet of 
oxygen, which, if the air be pure, effects the combustion of one 
cubic foot of coal gas, emanating from coals in the process of 
combustion in a furnace ; but if this quantity of air does not 
contain this 20 per cent., or one-fifth, of oxygen, it is clear we 
cannot obtain it. The air, in this case, may be said to be viti- 
ated, or impure. It is therefore desirable that the air admitted 
into a furnace should be direct from the atmosphere ; otherwise, 
the oxygen contained may be deficient, although the volume 
of air admitted be sufficiently large. 



PRINCIPLES OF COMBUSTION. 147 

Let us now inquire how far the ordinal*}* mode of constructing 
and managing our furnaces enables us to satisfy this condition. 

In ordinary furnaces, the supply of air is obtained by means 
of the ash-pit ; and the larger the ash-pit, the greater the quan- 
tity of air admitted. The ash-pit is made larger, under the 
mistaken notion that the more air we give, the better will be the 
draught, the more complete the combustion, and the greater the 
quantity of heat produced. 

There can scarcely be a more absurd practice than is involved 
in this one-sided view of the principles of combustion, even sup- 
posing that the introduction of air is tantamount to the introduc- 
tion of oxygen. It is manifest, however, that there are two 
different processes going on in the furnace, and two different 
combustibles, requiring their respective volumes of oxygen to 
consume them, namely, the gas or smoke generated in the body 
or cavity of the furnace, and passing off by the flues, and also, 
the solid carbon resting on the bars, both of which require sepa- 
rate volumes of oxygen to effect their combustion. 

All that seems to be concluded in practice is, that air is 
essential to combustion ; and that if air be admitted to the fuel, 
through between the bars, it will work out the process of com- 
bustion satisfactorily in its own way. And hence the many 
errors and absurdities of the present system of practice. 

There can be no greater mistake than letting a large quantity 
of air act directly on the burning fuel, which acts like a blast 
upon the red-hot mass, driving off the gases more rapidly,, but 
also driving off the contained heat, and consuming the fuel with. 
unnecessary rapidity. 

It seems to be taken for granted, that if air, ly any means, be 
introduced to the fuel in the furnace, it will, as a matter of 
course, mix with the gas, or other combustible, in a proper man- 
ner, and assume the state suitable for combustion, whatever be 
the nature or state of such fuel, and without regard to time or 
other circumstar,:es. Xow, it might as well be supposed, that 
by brinsring large masses of nitre, sulphur, and charcoal to- 
gether, we could form gunpowder. We know that it is by the 
proper mixture and incorporation of the different elementary 
atoms that simultaneous action is imparted to the whole ; and 
13* 



148 HEATING. 

so, also, by bringing different kinds of gases into a state of 
preparation for simultaneous action. 

The complete combustion of a body depends upon the 
chemical union of its atoms, or elementary divisions, with their 
respective equivalents of the supporter, oxygen; and which 
necessarily implies the bringing together, and the mixing of 
such atoms, previous to the mixture being fired for combustion. 

It is not our purpose to enter upon the theory of atomic mix- 
tures, or the time required to effect their combination, — which 
will be found in the numerous chemical works of the present 
day. We will now proceed to consider the means by which air 
may be introduced to the furnace, to effect the combustion of the 
gases therein generated. 

In looking for a remedy for the evils arising out of the hurried 
state of things which the interior of a furnace naturally presents, 
and observing the means by which the gas is effectually con- 
sumed in the Argand lamp, it seemed manifest, if the gas in the 
furnace could be presented by means of jets to an adequate 
quantity of air, as it is in the lamp, the result would be the 
same, — namely, a quicker and more intimate mixture and diffu- 
sion, and consequently a more extensive and perfect combustion. 
The difficulty of effecting a similar distribution of the gas in 
the furnace, by means of jets, however, seems insurmountable. 
One alternative alone remains : since the gas cannot be intro- 
duced by jets into the body of the air, the air might be intro- 
duced by jets into the body of the gas ; and this will be an 
effectual remedy. 

Fig. 33 is a section of Williams' furnace for the prevention 
of smoke. In this furnace, the fuel, as will be seen from the 
cut, is thrown immediately upon the grate bars, and through 
them the air finds admission to it for the purpose of consump- 
tion. The gases pass over the bridge C ; here they meet a cur- 
rent of air entering just beyond the bridge, which has been 
admitted by the air-tube b, below the ash-pit /, into the air- 
chamber d, and from thence escaping through a great number 
of small apertures in the diffusion plate above. 

The force with which the air enters through this series of 
jets or blow-pipes enables it to penetrate into the gases, and 






HEATING. 



149 



Fisr. 33. 




150 HEATING. 

obtain the largest possible extent of contact-surfaces for the air 
and gases ; which is important, since the short time allowed for 
the diffusion would otherwise be insufficient, in consequence of 
the rapid passage of the smoke and gases over the diffusion 
plates ; e is the spy-hole for ascertaining the state of the smoke. 

Fig. 34 is an apparatus invented by Mr. Jeffreys, of Bristol, as 
long ago as 1824, for precipitating the lamp-black, metallic 
vapors, and other sublimated matters from smoke, by washing 
the latter by means of a stream of water. Where the necessary 
supply can be secured, this plan is both effectual and economi- 
cal, and well adapted for situations where the presence of smoke, 
as well as the impurities produced by it, is an annoyance. 

In the vertical section, B B is the smoke flue. The smoke 
passing in the direction of the arrows at A, the flue turns down- 
ward; and at the top of this vertical portion is a cistern E, the 
perforated bottom of which lets down a constant stream of 
water, after it is set to work. The shower, in its descent, carries 
all the smoke and the sublimated matter which has passed from 
the fire, which runs off at the bottom, F. The flue may then 
turn upwards, or enter a common chimney ; but little or nothing 
will pass up it, providing the water be kept constantly running. 
This apparatus is easily constructed, and is admirably suited for 
hot-houses situated in the midst of pleasure-grounds, where 
smoke is unsightly and disagreeable. 

Whether these methods of consuming the gases generated in 
the furnaces and flues of hot-houses may be considered worthy 
of general adoption, we cannot tell. It is, nevertheless, pre- 
sented to the consideration of the ingenious mechanic, not 
doubting that were the subject fully taken up by energetic fur- 
nace builders, something good would be the result. That 
immense quantities of fuel are wasted by imperfect combustion, 
cannot be doubted, when we see the dense volumes of smoke 
proceeding from chimneys where much heat is required. 

Professor Brande says, " when air is admitted in front of the 
furnace, or through or over the fuel, it obviously never can 
effect those useful purposes, which are at once obtained by 
admitting it in due proportion to the intensely heated inflamma- 
ble vapors and gases, or, in other words, to the products of the 






HEATING. 



151 



Fig. 34. 



■ y~- ' ' •'■ ''-"■■"•---■- l: _^_ 





152 HEATING. 

distillation of coal, at such temperatures that they may take fire 
in its contact." If a number of jets of air be admitted into a 
heated inflammable atmosphere, as the body of a furnace, its 
combustion will be attained in such a way as to produce a great 
increase of heat, and, as a necessary consequence, destroy the 
smoke. 

In some of the large gardens of Europe, as well as in some 
manufactories, attempts have been made to consume the smoke 
or gases of the furnaces, by bringing them in contact with a body 
of glowing incandescent fuel, producing a result the reverse of 
what was expected, namely, the absorption of heat by their 
expansion and decomposition, instead of giving out heat by their 
combustion. It is strange that this erroneous notion should be 
persisted in, even at the present day, when any chemical work 
of good authority would satisfy any one wishing for such knowl- 
edge that decomposition, not combustion, is the effect of a high 
temperature being applied to hydro-carbon-gases ; — that no 
possible degree of heat can consume carbon ; — that it is a well- 
known property of both the varieties of carburetted hydrogen, 
that they deposit charcoal, (carbon) virtually become smoke, 
when heated ; — that the amount of carbon deposited is propor- 
tioned to the increase of temperature, and that its combustion is 
merely produced by, and is, in fact, its union with, oxygen, 
which these smoke-burners take no care to provide.^ 

* Numerous methods have been devised for burning smoke, and 
patents have been issued for supposed inventions of this kind, showing 
the want of chemical knowledge on this subject. One consists in hav- 
ing a double set of fire-bars, so that when the fuel is red-hot, it is 
thrown back on the innermost bars, and the smoke of the fresh coal in 
front passing over this incandescent fuel, is supposed to be consumed in 
its passage. Another proposes a sliding carriage for this purpose, 
working on castors inside the furnace. Others of a similar kind have 
been put forward, and all on the same principle ; all manifesting the 
same neglect or ignorance of chemistry, — for chemistry teaches us 
that heat has nothing to do with the combustion of smoke beyond this, — 
that a certain temperature is essential to the development of chemical 
action between the combustible and the supporter, when they are 
brought together. But producing heat is not producing air • and decom- 
position is not, in this respect, combustion. 



PRINCIPLES OF COMBUSTION. 153 

The neglect of chemistry when treating of combustion, and 
the results of this neglect in these smoke-burning furnaces, can- 
not be too strongly exposed ; neither can its study be too strongly 
enforced, seeing that it is practically within the reach of all. 
For chemistry is no longer the mysterious alchemy that it was 
a century ago ; it is now a mere rigid inquiry into nature's pro- 
cesses and laws, by the aid of those proofs and illustrations 
which nature herself has supplied. It has taken its place among 
the exact sciences, and now recognizes no man's dictum or opin- 
ion, apart from experimental tests, and strict, substantial evidence. 

Looking, then, to chemistry, we "would add, in reference to 
these smoke-burning expedients, that, in seeking to obtain heat 
from gas, (or smoke,) the bringing it into connection with ignited 
carbonaceous matter, or to anything approaching the temper- 
ature of incandescence, is absolutely useless, if not injurious, 
until we are assured of having the means of contact with air 
fully provided for. 

The mere enunciation of a plan " for consuming smoke" is 
prima facie evidence that the inventor has not studied and con- 
sidered the subject in its chemical relations. Chemists can 
understand a plan for the prevention of smoke ; but as to its 
combustion^ it is so unscientific, not to say impossible, (if there 
be any truth in chemistry,) that such phraseology should be 
avoided. The popular phrase, " A furnace burning its own 
smoke," may be justifiable, as conveying an intelligible mean- 
ing ; but, in a work having any pretensions to science, or from 
any one pretending to teach those who are unable to distinguish 
for themselves, and who may easily be led into error, is wholly 
objectionable. 

6. Construction of Furnaces. — From what has been already 
said, in the preceding part of this section, it will be seen that 
the construction of furnaces is a matter of great importance in 
the economy of heat. To investigate the various varieties of 
furnaces which have been recommended, would occupy too much 
of our space at present, especially as we shall have to refer to 
them hereafter, when treating of the different methods of heat- 
ing; besides, in small apparatuses, the intense heat required 



154 HEATING. 

for large boilers is unnecessary. A very moderate heat, ap- 
plied on the most economical principle, and the furnace so con- 
structed as to make the fuel burn for a long time, without much 
attention, and without much escape of smoke, is the grand 
desideratum, and which is easily accomplished, with a moderate 
degree of care and skill in the erection. 

Passing over, then, as unnecessary for our purpose at present, 
the many ingenious forms which have been given to furnaces, 
we will proceed to describe the most simple plan, which, in our 
experience, is the most effectual in the combustion of the fuel, 
as well as the least expensive in the construction. 

It should be an object, of consideration, in building the fur- 
nace, to confine the generated heat within the cavity of the 
furnace as much as possible, so that the gases generated by the 
combustion of fuel may be prevented from passing too rapidly 
along the flue ; this is more especially requisite with boiler 
furnaces. The throat of the furnace should be contracted as 
much as possible. In furnaces where the only entrance for air 
is by the bars, provision should be made for the entrance of 
enough — but no more than enough — for the combustion of 
the fuel, and the entrance should, in all cases, be regulated by 
a damper, on the ash-pit door. It should be considered, that 
the rarity of the heated gases causes them to force their pas- 
sage through the throat of the furnace, just in the proportion 
of its size. 

We have already shown that any air entering through the 
door of the furnace reduces the intensity of the heat, although 
it is supposed by some that the passage of air over the burning 
fuel promotes the more perfect combustion of the gaseous pro- 
ducts of the -coal. But even if this be correct, the heat will be 
reduced, and less heat will be generated in a given time, than 
if the whole gaseous products escaped by the chimney. 

The kind of fuel to be burnt must, in all cases, determine 
the width of the bars ; and as a certain open area is necessary 
for the admission of air to effect combustion, it is desirable that 
this area should be known. 

Supposing the ordinary kind of furnace bars to afford about 
thirty inches of opening for air for every square foot of surface, — 



PRINCIPLES OF COMBUSTION. 155 

then supposing you wish to erect a hot water apparatus — the 
relative proportions between the area of the bars and the length 
of pipe would be as follows : — 

Area of Bars. 4 inch pipe. 3 inch pipe. 2 inch pipe. 

75 square inches will supply 150 feet, or 200 feet, or 300 feet. 

100 " " " " 200 " 266 " 400 

150 " " " " 300 " 400 " 600 

200 " " " " 400 " 533 " 800 " 

250 " « " " ' 500 " 666 " 1000 ' 

300 " " " " 600 " 800 " 1200 ' 

400 " " " " 800 " 1066 " 1600 ' 

500 " " " " 1000 " 1333 " 2000 ' 

Thus, suppose there are six hundred feet of pipe, four inches 
in diameter, in an apparatus, — then the area of the bars should 
be three hundred square inches, so that thirteen inches in 
breadth, and twenty-three inches in length, will give the re- 
quired quantity of surface. When it is required to obtain the 
greatest heat in the shortest time, the area of the bars may be a 
little increased. 

In order to make the fire burn for a long time without atten- 
tion, the furnace should extend bej'ond the bars, both in length 
and breadth ; and the coals, which are placed on this blank part 
of the furnace, in consequence of receiving no air from below, 
will burn slowly, and will only enter into complete combustion 
when the rest of the coal, on the bars, has been consumed. 

It may be observed, that as the maximum effect of the furnace 
is seldom required, the register on the ash-pit door, and the 
damper in the flue, must be used to regulate the draught, and 
thus limit the consumption of fuel. 
14 



SECTION II. 

PRINCIPLES OF HEATING- HOT-HOUSES. 

1. Effects of artificial heat. — The effects that are produced 
upon the functions of vegetables, by atmospheric air that has 
passed over intensely heated surfaces, are perceptible to the 
most casual observer. The changes, therefore, that are produced 
upon atmospheric air by subjecting it to a high temperature, are 
of the utmost importance to the horticulturist, and consequently 
demand our particular attention. 

When common air passes over highly heated surfaces, the 
small particles of animal and vegetable matter, (organic mat- 
ter,) which are always held in suspension by it, are decomposed 
by the heat, and resolved into various elementary gases. This 
is one of the causes of the unpleasant smell which results from 
this method of heating, as in common stoves, Polmaise furnaces, 
&c. But, in addition to this, the aqueous vapors of the atmos- 
phere are almost entirely decomposed, the oxygen entering into 
combination with the iron, and the hydrogen mixing with the 
air. The changes which have thus taken place, render the 
atmosphere extremely deleterious to both animal and vegetable 
life. 

The mixture of the hydrogen thus disengaged is even more 
injurious to the plants than the alteration which has taken place 
in its hygrometric state, as this will be partly supplied by the 
moisture contained in their tissue, until it be restored to the 
atmosphere by evaporation, which is easily effected. 

The particles of animal and vegetable matter — as we have 
said — are decomposed by the heat; and they then produce 
extraneous gases, consisting of sulphuretted, phosphuretted, and 
carburetted hydrogen, with various compounds of nitrogen and 



PRINCIPLES OF HEATING HOT-HOUSES. 157 

carbon, which, in the state in which they exist, are highly inim- 
ical to vegetable life. ^ 

The quantity of hydrogen which is eliminated by the decom- 
position of water contained in the air is one thousand three hun- 
dred and twenty-five cubic inches for every cubic inch of water 
that is decomposed ; and if the dew point of the air be 45° at an 
average, this quantity will be given out from every seventy-two 
cubic feet of air which passes over the heated surface. It is, 
therefore, not difficult to account for the effects produced on 
vegetation by hot-air stoves, in consequence of the air, when 
thus artifically dried, abstracting too much moisture from their 
leaves. It is also clear that the injury must increase in propor- 
tion to the length of time the apparatus continues in use, by the 
plants being surrounded by, and compelled to inhale, these extra- 
neous gases, which are evolved from the decomposition of the 
constituents of the atmosphere. 

The extreme dryness of the air, after it has been deprived of 

# I am unable to ascertain the exact nature and extent of the change 
which atmospheric air undergoes by being passed over intensely heated 
metallic bodies ; but whatever be the chemical alteration which occurs, 
a physical change undoubtedly takes place, by which its electrical con- 
dition is altered. 

From some experiments recorded in the Philosophical Transactions of 
the Eoyal Society, made with a view of ascertaining the effect produced 
on the animal economy by breathing air which has passed through 
heated media, it appears that the air which has been heated by metallic 
surfaces of a high temperature must needs be exceedingly unwholesome. 
A curious circumstance is related, in reference to these experiments, 
which is illustrative of this fact. 

" A quantity of air, which had been made to pass through red-hot 
iron and brass tubes, was collected in a glass receiver, and allowed to 
cool. A large cat was then plunged into this air, and immediately she 
fell into convulsions, which, in a minute, appeared to have left her 
without any signs of life ; she was, however, quickly taken out and 
placed in the fresh air, when, after some time, she began to move her 
eyes, and, after giving two or three hideous squalls, appeared slowly to 
recover. But on any person approaching her, she made the most violent 
efforts her exhausted strength would allow to fly at them ; insomuch, 
that, in a short time, no one could approach her. In about half an hour 
she recovered, and became as tame as before." 



158 PRINCIPLES OF HEATING HOT-HOUSES. 

its hygrometric vapor by passing over a hot-air stove, such as 
polmaise, is productive of the worst consequences to growing 
plants. To remedy this evil, a trough of water is laid over the 
heating surface, which m some degree mitigates this evil. The 
evil, however, cannot be entirely got rid of by this means ; for 
even if the proper quantity of moisture can be again restored to 
the air, the effects which result from the use of extraneous 
gases are in no way removed. When the surface of radiation is 
an iron plate, these injurious effects are much greater. 

The heating by means of brick flues is, in some respects, 
similar to the effects produced by hot-air stoves, but only when 
the flues are heated to a high temperature, which is unneces- 
sary. In the latter case, an unwholesome smell is also produced, 
by the decomposition of the organic matter in the atmosphere, 
and in some cases, probably, by a small portion of sublimed 
sulphur from the bricks, as well as by the escape of various 
gases through the joints or accidental fissures of the flues. 
These contingent causes may, however, be in a great measure 
avoided. The hygrometric vapors of the atmosphere are not 
decomposed by this system of heating, as by a hot-air stove, 
because when the flues are warmed to a common temperature, 
the heat is perfectly pure, and the materials of which the flues 
are built having but little affinity for oxygen, they are conse- 
quently more healthy than hot-air stoves. 

Air passing over a highly heated surface of iron is, therefore, 
more injurious than when passed over any other body, as stone, 
or brick, as the power of iron to decompose water increases with 
the temperature to which it is heated. The limit to which the 
temperature of any metallic surface ought to be raised, for warm- 
ing horticultural buildings, (or indeed any other buildings,) is 
212°, if a healthy, uncontaminated atmosphere be desired. The 
importance of this rule cannot be too strongly insisted on, for 
upon it entirely depends the healthiness of every system of 
artificial heat. 

2. Laws of Heat. — Heated bodies give off their caloric by 
two distinct methods — radiation and conduction. These are 
governed by different laws ; but the rate of cooling — or parting 



PRINCIPLES OF HEATING HOT-HOUSES. 159 

with heat — by both modes, increases in proportion as the 
heated body is of greater temperature above the surrounding 
medium. 

The cooling of a heated body, under ordinary circumstances, 
is evidently the combined effects of radiation and conduction; 
the conductive power of the air is, evidently, owing to the ex- 
treme mobility of its particles, for otherwise it is one of the 
worst conductors with which we are yet acquainted, so that 
when confined in such a manner as to prevent its freedom of 
motion, it becomes useful as a non-cond actor. 

The proportion which radiation and conduction bear to each 
other has, in general, been very erroneously estimated. Count 
Rumford considered the united effect, compared with radiation 
alone, was as five to three, and Franklin supposed it to be as 
five to two. 

No such general law, however, can be deduced, for the relative 
proportions vary with the temperature, and with the peculiar 
substance, or surface, of the heated body ; for, while the cooling 
effects of the air, by conduction, is the same on all substances, 
and in all states of the surface of those substances, radiation 
varies very materially, according to the nature of the surface. 

The influence of the air, by its power of conduction, varies 
also with its elasticity. The greater its elastic force, the greater 
also is its power of cooling, according to the following law : — 
When the elasticity of the air varies in a geometrical progres- 
sion whose ratio is 2, its cooling power also changes in a geo- 
metrical progression whose ratio is 1.366. 

The same law holds with all gases, as well as with atmos- 
pheric air ; but the ratio of the progression varies with each gas. 

To show the relative velocities of cooling at different temper- 
atures, the following table, constructed from the experiments of 
Petit and Dulong, is given. The first column shows the excess 
of temperature of the heated body above the surrounding air ; 
the second column shows the rate of cooling of a thermometer 
with a plain bulb, and the third column gives the rate of cooling 
when the bulb was covered with silver leaf. The fourth column 
shows the amount due to the cooling of the air alone ; and by 
deducting this from the second and third columns respectively, 
14* 



160 



PRINCIPLES OF HEATING HOT-HOUSES. 



we shall find what is the amount of radiation under the two 
different states of surface, noticed at the top of the second and 
third columns. * 



Excess of temperature 
of the thermometer 


Total velocity of 


Total velocity of cool- 


Amount of cooling due 


above that of the air. 


cooling of the na- 


ing of the bulb cov- 


to conduction of air 


Centigrade Scale. 


ked bulb. 


ered with silver leaf. 


alone. 


260° 


24-42 


10-96 


8-10 


240° 


21-12 


9-82 


7-41 


220° 


17-92 


8-59 


6-61 


200° 


15-30 


7-57 


5-92 


180° 


13-04 


6-57 


5-19 


160° 


10-70 


5-59 


4-50 


140° 


8-75 


4-61 


3-73 


120° 


6-82 


3-80 


3-11 


100° 


5-57 


3-06 


2-53 


80° 


4-15 


2-32 


1-93 


60° 


2-86 


1-60 


1-33 


40° 


1-74 


•96 


•80 


20° 


•77 


•42 


•34 


10° 


•37 


•19 


•14 



Some very remarkable effects may be perceived by an inspec- 
tion of the above table. It appears that the ratio of heat lost by 
contact of the air alone, is constant at all temperatures ; that is, 
whatever is the ratio between 40° and 80°, for instance, is also 
the ratio between 80° and 160°, or between 100° and 200°. 
This law is expressed by this formula : 

v = n. t vi33 '> 

where t represents the excess of temperature, and n a number 
which varies with the size of the heated body. In the case 
represented in the foregoing table, n === 0.00857. 

Another remarkable law, is that the cooling effect of the air is 
the same, for the like excess of heat, on all bodies, without 
regard to the particular state or nature of their surface. This 

* The temperatures of this table are expressed in degrees of the Cen- 
tigrade thermometer, as the zero of this thermometer is the freezing 
point of water, and from that to the boiling point of the same fluid is 
100°. In order to find the number of degrees on Fahrenheit's scale, 
which answers to any given temperature of the Centigrade, multiply 
the number of degrees of Centigrade by 9, and divide the product by 5 ; 
add 32 to the quotient thus obtained, and this sum will be the number 
of degrees of Fahrenheit required. 






PRINCIPLES 0*F HEATING HOT-HOUSES. 161 

was ascertained by Petit and Dulong, in a series of experiments, 
not necessary here to detail, bat which proved the accuracy of 
the deduction. 

By comparing the second and third columns of the above 
table, it will be immediately perceived that the loss of heat by 
radiation varies greatly, with the nature of the radiating sur- 
face ; though, whatever be the nature of the surface, the loss of 
heat is the same in all cases, though in a different ratio. 

It should be observed, that, in this table, the second, third, 
and fourth columns show the number of degrees of heat which 
were lost per minute by the body which was subject to the 
experiment ; and, therefore, these numbers represent the velocity 
of cooling. 

The fact, already adverted to, that the ratio of cooling in 
those bodies that radiate least is more rapid at low tempera- 
tures, and less at high temperatures, than those bodies that 
radiate most, is, perhaps, one of the most remarkable of the laws 
of cooling. It was first deduced experimentally by Petit and 
Dulong, and it may be mathematically proved from their for- 
mula ; but it is unnecessary here to enter into the investigation. 
It appears, however, that when the total cooling of two bodies is 
compared, the law is more rapid at low temperatures for the 
body which radiates least, and less rapid for the same body at 
high temperatures ; though separately, for conduction and radia- 
tion, the law of cooling is, for the former, irrespective of the 
nature of the body, and for the latter, that all bodies preserve at 
every difference of temperature a constant ratio in their radi- 
ating power. 

It is not our purpose to enter minutely into detail on the laws 
of heat, which will be found in modern works on chemistry, 
and which ought to form part of the studies of all young gar- 
deners who wish to become acquainted with the principles of 
hot-house management. We will now proceed to consider the 
specific properties of air and water as agents in the heating of 
horticultural structures. 

3. Specific heat of air and water. — Very erroneous notions 
are entertained by many persons as to the absolute quantity of 



162 PRINCIPLES OF HEATING HOT-HOUSES. 

heat taken up by different substances. To ascertain, therefore, 
the effect a certain quantity of water will produce in warming 
the air of a hot-house, there appears to be no better method 
than that of computing from the specific heat of gases compared 
with water. 

Every substance has its peculiar specific heat. Now, one 
cubic foot of water, by losing one degree of heat, will raise the 
temperature of 2990 cubic feet of air the extent of one degree ; 
and, by the same rule, by losing 10° of its heat, it will raise the 
temperature of 2990 cubic feet of air 10 degrees; and so with 
similar quantities in similar proportions. 

In order to know the time it will take to heat a certain quan- 
tity of air any required number of degrees, by means of hot 
water contained in metal pipes, we must calculate the effect 
from direct experiment ; and, as the radiating and conducting 
powers of different substances differ considerably, it is necessary 
that the experiment be made with the same material as the 
pipes for which we wish to estimate the effect. 

From data obtained by experiments on the cooling of iron 
pipes, it appears that the water contained in a pipe 4 inches in 
diameter loses -851 of a degree of heat per minute, when the 
excess of its temperature is above 125 degrees above that of the 
surrounding air. There one foot in length of a pipe 4 inches 
diameter will heat 222 cubic feet of air one degree per minute, 
when the difference between the temperature of pipe and the 
air is 125 degrees. 

To calculate from this data, however, the length of a pipe, of 
any given size, that will be necessary to warm a house, and to 
maintain it at any given temperature under a certain external 
temperature, it will be necessary to estimate the heat lost by 
the conducting and radiating power of the glass, and of any 
metallic substance used in the structure. 

Heating horticultural structures is a very different matter 
from heating solid opaque buildings ; and here many erectors 
of heating apparatus fall into error. They suppose, because an 
apparatus of certain power heated a large building, — a church 
or a hall, — one of proportionate dimensions should warm a hot- 
house of proportionate size, without taking into full considera- 



PRINCIPLES OF HEATING HOT-HOUSES. 163 

tion the great difference of the external radiation, and the con- 
duction of heat by the materials of the building. 

The loss of heat by buildings covered with glass is very great. 
It appears, by experiment, that one square foot of glass will cool 
down 1-279 cubic feet of air as many degrees per minute as the 
internal temperature of the house exceeds the temperature of 
the external air; thus, if the difference between the external 
temperature and the temperature of the house be 30 degrees, 
then 1-279 cubic feet of air will be cooled 30 degrees by each 
square foot of glass ; or, more correctly, as much heat as is equal 
to this will be given off by each square foot of glass, for, in real- 
ity, a very much larger quantity of air will be affected by the 
glass, but it will be cooled to a less extent. The real loss of 
heat, however, from the house will be what is here stated. 

There are various causes likely to affect these calculations, 
such as, — 

High winds, which are found to reduce the internal tempera- 
ture more than actual cold, or even frost ; 

Condensation of moisture on the glass, which prevents the 
escape of heated air ; and, when a certain temperature is main- 
tained within, prevents radiation from the glass to a great 
degree ; 

The extent of wood in the roof of the house, which also pre- 
vents radiation and conduction, as in the case of metallic roofs. 

These circumstances will be found to affect, in a greater or 
less degree, the air of the house, though, under general circum- 
stances, these calculations will be nearly correct. 

In estimating the quantity of glass surface contained in a 
building, the extent of wood surface must be carefully excluded. 
This is particularly necessary in all horticultural buildings, 
where the maximum of heating power is dependent upon the 
estimate taken. The readiest way of calculating, and suffi- 
ciently accurate for ordinary purposes, is to take the square sur- 
faces of the sashes, and then deduct one eighth of the amount for 
wood work. In the generality of horticultural buildings, the 
wood work fully amounts to this quantity. When the frames 
and sashes are made of metal, the radiation of heat will be quite 



164 



PRINCIPLES OF HEATING HOT-HOUSES. 



as much from the frame as from the glass ; therefore no deduc- 
tion is required in such cases. 

From the preceding calculations the following corollary may 
be drawn : — 

The quantity of air to be warmed per minute in habitable 
rooms and public buildings, must be 3^ cubic feet for each 
person the room contains, and 1^- cubic feet for each square 
foot of glass. 

For conservatories, forcing-houses, and all buildings of this 
description, the quantity of air warmed per minute must be l£ 
cubic feet for each square foot of glass the structure contains. 

When the quantity of air required to be heated has thus been 
ascertained, the length of pipe to heat it by hot water may be 
found by the following table : 



Table of the quantity of pipe 4 inches diameter which will heat 1000 cubic 
feet of air per minute, any required number of degrees. The temperature 
of the pipe being 200° Fahrenheit : — 



Temperature of 
rial air. 


exter- 


Temperature at which the house is required to be kept. 


Fahrenheit's 


scale. 


45° 


50 J 


55° ! 60° 


65° | 70° | 75° | 80° | 85° | 90° 




10° 


126 


150 


174 


200 


229 


259 


292 


328 


367 


409 




12° 


119 


142 


166 


192 


220 


251 


283 


318 


357 


399 




14° 


112 


135 


159 


184 


212 


242 


274 


309 


347 


388 




16° 


105 


127 


151 


176 


204 


233 


265 


300 


337 


378 




18° 


98 


120 


143 


168 


195 


225 


256 


290 


328 


368 




20° 


91 


112 


135 


160 


187 


216 


247 


281 


318 


358 




22° 


83 


105 


128 


152 


179 


207 


238 


271 


308 


347 




24° 


76 


97 


120 


144 


170 


199 


229 


262 


298 


337 




26° 


69 


90 


112 


136 


162 


190 


220 


253 


288 


327 




28° 


61 


82 


104 


128 


154 


181 


211 


243 


279 


317 




30° 


54 


75 


97 


120 


145 


173 


202 


234 


269 


307 


Freezing point 32° 


47 


67 


89 


112 


137 


164 


193 


225 


259 


296 




34° 


40 


60 


81 


104 


129 


155 


184 


215 


249 


286 




36° 


32 


52 


73 


96 


120 


149 


175 


206 


239 


276 




38° 


25 


45 


66 


88 


112 


138 


166 


196 


229 


266 




40° 


18 


37 


58 


80 


104 


129 


157 


187 


220 


255 




42° 


10 


30 


50 


72 


97 


121 


148 


178 


210 


245 




44° 


3 


22 


42 


64 


85 


112 


139 


168 


200 


235 




46° 




15 


34 


56 


79 


103 


130 


159 


190 


225 




48° 




7 


27 


48 


70 


95 


121 


150 


181 


215 




50° 






19 


40 


62 


86 


112 


140 


171 


204 




52° 






11 


32 


54 77 


103 


131 


161 


193 



To ascertain, by the above table, the quantity of pipe required 
to heat 1000 cubic feet of air per minute, find, in the first column, 



PRINCIPLES OF HEATING HOT-HOUSES. 



165 



the temperature which corresponds to that of the external air, 
which may be the medium (or average) of your locality. 
Then, in the other column, find the temperature required in the 
house ; then, in this latter column, and on the line which cor- 
responds with the external temperature, the required number of 
feet of pipe will be found. 

Supposing, now, that a forcing-house is to be kept at 75 de- 
grees, and the average of the external thermometer in the 
coldest weather, taken at 10° (Fah.) ; then, by the foregoing 
table, we find, under the column 75°, and on the line 10°, for 
external temperature, the quantity 292, which is the number of 
feet of pipe required to heat 1000 cubic feet of air per minute, 
the proposed number of degrees. Of course, the volume of air 
in the house must be previously ascertained. Any other differ- 
ence of temperature may be found in the same way. 

It will thus be perceived, that the amount of heat required 
for warming a glazed structure is much greater than that re- 
quired for warming an opaque building of the same size, in 
consequence of the radiation of heat from its surface ; and the 
difference is much greater than the allowance made by erectors 
of heating apparatuses, under general circumstances. 

To ascertain the effect of glass windows in cooling the atmos- 
phere of a house, the following experiments were made, with a 
vessel as nearly as possible the same thickness as the glass 
ordinarily used for glazing. The temperature of the house, in 
these experiments, was 65° ; the thickness of the glass was .0825 
-of an inch ; the surface of the vessel measured 34-296 square 
inches, and it contained 9*794 cubic inches of water. The time 
in which this vessel cooled, when filled with hot water, is shown 
as follows : — 



Thermometer 
cooled. 


Observed 
time of 
cooling. 


Calculated 
time of 
cooling. 


Average rate of the 

observed time of 

cooling. 


from to 


150° 
150 
150 
150 


140° 
130 
120 
110 


6' 40" 
14 50 
23 30 
34 


& 54" 
14 43 
23 40 
34 


1-176 3 per minute, 
at an excess of 65° 
above the tempera- 
ture of the air. 



From the average rate of cooling here given, the effect of 
glass in cooling the atmosphere of a room may easily be calcu- 



166 PRINCIPLES OF HEATING HOT-HOUSES. 

lated, as the specific heat of equal volumes of air and water is 
as 1 to 2990. The above average will show that each square 
foot of glass will cool 1-279 cubic feet of air one degree per 
minute, when the temperature of the glass is one degree above 
that of the external air. 

But by this we can only find the effect of glass in a still at- 
mosphere, and, therefore, to find the effect of glass in cooling 
the volume of a hot-house, especially when exposed to the action 
of winds, further experiments are necessary, of which we shall 
treat in a subsequent part of this work, in connection with " pro- 
tection of hot-house roofs during the night." 



SECTION III. 

HEATING BY HOT WATER, HOT AIR, AND STEAM.. 

1. The practice of employing hot water, circulating through 
metallic tubes, or wooden troughs, for diffusing artificial heat in 
horticultural structures, though of recent origin, has now become 
so general, that its merits are fully acknowledged as the best 
method that has yet been invented, to effect the purpose with 
efficiency and economy. Until the last few years, — although 
its powers and properties were fully known, — it had been 
chiefly confined to a few cases of experiment, rather than to any 
general or useful purpose. 

The present day, however, has fully revealed its merits, and 
shown the great, the unlimited, extent of its practical application 
and general utility. When we see such an immense structure 
as the great Palm house, lately erected at Kew Gardens, in 
London, heated with hot water in preference to all other modes ; 
when we see the lately applauded mode of heating by steam 
abandoned; when we see the powerful, but unsuccessful, at- 
tempt to establish a new system of heating by hot air, called 
Polmaise, by some of the first horticulturists of England ; when 
we see this system, notwithstanding its powerful supporters, 
driven into obscurity, and all but annihilated, by the well-tried 
superiority of hot water, which maintains its proud preeminence 
over all other methods of heating, and has its superiority ac- 
knowledged, even by its enemies. 

One of the greatest advantages which this mode of heating 
possesses over all others, is, that a greater permanency of tem- 
perature can be obtained by it, than by any other method. The 
difference between an apparatus heated by hot water, and one 
heated by steam, is not less remarkable, in this particular, than 
in its superior economy of fuel. 
15 



168 HEATING BY HOT WATER, HOT AIR, AND STEAM. 

2. Comparison of heat in water and steam. — The heating of 
horticultural buildings by steam had its day and its admirers, 
though both are now numbered among the things that were. 
Even if the original outlay were equal, the additional outlay for 
fuel, the risk of explosion from neglect, and the want of perma- 
nency in the apparatus to maintain the heat for any length of 
time, are insuperable objections to its adoption. Among many 
instances that could be given of this method of warming large 
houses, we might mention the large Palm house, in the Royal 
Botanic Garden of Edinburgh, which was erected when heating 
by steam was in the height of its fame. This house is about 
fifty feet high and seventy-five feet wide, in the form of an 
octagon; the pipes are laid around the side of the wall. There 
is a contrivance, however, resorted to here, in connection with 
the system, to which its success in heating the house may be 
somewhat, if not entirely, attributed. The steam is thrown into 
large iron boxes, loosely filled with stones and pieces of brick, 
for the retention and absorption of the heat. These iron boxes 
are placed underneath the shelf that surrounds the house, and 
close by the side of the wall, and at regular distances from 
each other. By this contrivance, the temperature of the house 
is kept up for a considerable time longer than would be by the 
circulation of the steam alone. Indeed, we believe it was found 
perfectly impracticable to maintain the proper temperature, dur- 
ing cold nights, until this expedient was adopted, viz., of filling 
the boxes with absorbing materials. 

We have known conservatories, in which steam apparatuses 
had been erected, taken down, and their place supplied with 
others of hot water, merely in consideration of the consumption 
of fuel and extra attention required by a steam apparatus, keep- 
ing the danger of explosion out of the question. 

It seldom happens that the pipes of a hot-water apparatus can 
be raised to so high a temperature as 212° ; in fact, it is not 
desirable to do so, because it is unnecessary to generate steam, 
which would only escape by the air vent, without affording any 
available heat. Steam pipes, on the contrary, must always be 
above the temperature of 212°, otherwise steam will not be gen- 
erated ; and here the grand point to be attended to in artificia] 



HEATING BY HOT WATER, HOT AIR, AND STEAM. 169 

heating is nullified, namely, the diffusion of heat at a low tem- 
perature. A given length of steam pipe, however, will afford 
more heat than one heated by hot water, by the aggregate cal- 
culation of its specific heat. But, if we consider the relative 
permanency of temperature, we shall find a very remarkable dif- 
ference in favor of pipes heated by hot water ; and the calculations 
here given are fully confirmed by experience and observation. 

The weight of steam, at the temperature of 212°, compared 
with the weight of water at 212°, is about as 1 to 1694, so that 
a tube that is filled with water at 212° contains 1694 times as 
much matter as one of equal size filled with steam. If the 
source of heat be withdrawn from the steam pipes, the temper- 
ature will soon fall below 212°, and the steam immediately 
in contact with the pipes will condense ; but, in condensing, 
the steam parts with its latent heat, and this heat, in passing 
from the latent to the sensible state, will again raise the tem- 
perature of the pipes ; but, by the withdrawal of the heat from 
the boiler, the action of the cold air on the pipes quickly con- 
denses the whole of the steam contained in them, which, when 
condensed, possesses just as much heating power as the same 
bulk of water at a similar temperature. This water now occu- 
pies only -j-gV? P art °f tne space which the steam originally did 
in the pipes. 

The specific heat of uncondensed steam, compared with water, 
is, for equal weights, as -8470 to 1 ; but the latent heat of 
steam being estimated at 1000 degrees, we shall find the relative 
heat obtainable from equal weights of condensed steam and of 
water, reducing both from the temperature of 212° to 60°, to be 
as 7*425 to 1 ; but for equal bulks it would be as 1 to 228 ; that 
is, bulk for bulk, water will give out 228 times as much heat as 
steam, reducing both to the temperature of 60°. A given bulk 
of steam, therefore, will lose as much of its heat in one minute, 
as the same bulk of water will lose in three hours and three 
quarters. 

It must be considered, however, that when the water and 
steam are both circulated in iron pipes, the rate of cooling will 
be somewhat different from this ratio, in consequence of the 



170 HEATING BY HOT WATER, HOT AIR, AND STEAM. 

much larger quantity of heat contained in the metal, than in the 
steam with which the pipe is filled. 

The specific heat of cast iron being nearly the same as water, 
the water being 1000 and the iron 1100, if we take two similar 
pipes, four inches in diameter and one fourth of an inch thick, 
the one filled with water and the other with steam, each at the 
temperature of 212°, the one which is filled with water contains 
4-68 times as much heat as the one which is filled with steam. 
Therefore, if the pipe with the steam cools down to the temper- 
ature of 60° in one hour, the one filled with water would require 
four hours and a half, under the same circumstances, before it 
reached the like temperature. 

But this is merely reckoning the effect of the pipe and the 
fluid contained in it. In a steam apparatus, this is all that is 
effective in giving out heat ; but in a hot-water apparatus there 
is likewise the heat from the water contained in the boiler, and 
even of the brick-work around the boiler, all which tends to 
increase the heat of the pipes, long after the fire is extinguished. 
In the one, the heat will continue to circulate through the pipes 
as long as any heat remains about the fire-place, because the 
circulation will continue in the pipes until the whole apparatus 
is cooled down. But, in the case of steam pipes, as soon as the 
water in the boiler falls below the boiling point, (212°,) circula- 
tion ceases, and the pipes then begin to cool, the remaining heat 
in the boiler and furnace goes for nought. 

From these causes the difference in permanency of hot w r ater 
and steam will be clearly apparent, and the fact of a house 
heated with hot water keeping up its temperature at least six 
times as long as one heated with steam, will be fully understood 
by those interested in the matter. These considerations are of 
the utmost importance to those erecting horticultural build- 
ings, or, indeed, any other kind of buildings requiring artificial 
heat. This admirable property, which water possesses, of re- 
taining its heat, of carrying it to any distance, and, without 
difficulty, giving it out gradually, or retaining it for many hours, 
renders it of vast importance to gardeners, and prevents the 
necessity of that constant attention to the fire, which forms so 
serious an objection in all other methods of heating. 



HEATING BY HOT WATER, HOT AIR, AND STEAM. 171 

We find, by experience, that no system of heating horticul- 
tural buildings in all respects answers the purpose so well as a 
hot-water apparatus, well constructed, and judiciously arranged, 
in regard to the amount of work it has to do, so that it may not 
be necessary to strain it, on exigencies, to its maximum point of 
strength. In whatever point of view it may be regarded, it is, 
undoubtedly, the best for all practical purposes ; and the best 
possible evidence of its utility is derived from the fact, that no 
case has ever come under our knowledge, wherein it has failed 
to give complete satisfaction, when it has been properly con- 
structed, rightly managed, and judiciously arranged, in regard 
to supplying a sufficient amount of radiating surface for the 
work it has to do. 

3. Comparison of hot air with hot water, as a mode of heating 
horticultural structures. — Various erroneous opinions and prin- 
ciples have been theoretically and practically promulgated, in 
regard to hot-air heating ; and, carrying with them, in general, 
some degree of plausibility, and in some cases emanating from 
men of learning, have led many, who have not studied the mat- 
ter attentively, into very great errors. However invidious, 
therefore, may be the task of pointing out such errors, we con- 
sider it our duty, when treating on the subject at large, not only 
to exhibit what we consider to be the true principles, but to 
show where erroneous principles have been adopted. This must 
serve as an apology for the freedom with which the advocates 
of Polmaise, and other methods of hot-air heating, and the sys- 
tems they approve, are descanted on in this section. 

We have already observed that the cooling of a heated body, 
under ordinary circumstances, is evidently the combined effect 
of radiation and conduction. The conductive power of the air 
is principally owing to the mobility of its particles, for, otherwise, 
it is one of the worst conductors we are acquainted with. 

Atmospheric air, in passing into a house over a highly heated 
surface, must necessarily lose a large quantity of its contained 
moisture ; [see 1. Effects of Artificial Heat, of the preceding 
section;] and, as its capacity for taking up moisture is increased 
according to its temperature, it follows that a great demand 
15* 



172 HEATING BY HOT WATER, HOT AIR, AND STEAM. 

must be made upon the moisture of the house, upon the plants, 
and upon everything else within its influence capable of giving 
off moisture. This is also the case with hot-water pipes. But 
here the advantage of the latter is plainly illustrated ; for while 
a hot-air stove abstracts the moisture, in excess, from that part 
of the house nearest to the aperture of ingress, hot-water pipes 
radiate the heat at a low temperatw'e equally over the whole 
surface, and, as the temperature at which the heat is radiated is 
comparatively low, little or no moisture is abstracted. Some 
suppose that they get a fine moist heat from hot-water pipes. 
This, however sound and sensible it may appear, is, nevertheless, 
a practical fallacy, the fact of the case being this, — that, instead 
of the moisture of the house being taken up by the air, as in 
the case of Polmaise, and other stoves, the warm air of the 
pipes being so much lower in temperature than that of the 
stoves, it cannot take it up, and hence the moisture remains 
with the plants and the atmosphere in its original purity. In 
fact, there is no difference between the heat radiated from stone, 
brick, or iron, unless it be mixed with extraneous gases, by heat- 
ing these bodies to a high temperature. 

To supply the moisture required by the heated air, water may 
be placed in evaporating pans, in connexion with the current 
of ingress; but, as we have already shown, though moisture 
may be supplied, the hydrogen of the rarefied air still remains 
uncombined, and, until the air be replaced by a fresh volume 
from the external atmosphere, its impurities still remain. 

With regard to the motion and circulation of the atmosphere 
of a hot-house, the system of heating by hot air possesses, the- 
oretically, some advantages over all others. Strictly speaking, 
however, this has scarcely a practical foundation. If hot air be 
admitted in currents, the atmosphere will be agitated, certainly, 
but the house will be very unequally heated, as the heated air 
will pass upward in currents, at the aperture of its entrance, 
without diffusing itself over the lower surface of the house. 
Air expands, when heated, ¥ ^ of its bulk for each degree of 
Fahrenheit, and the velocity of its motion is equal to the addi- 
tional height which a given weight of heated air must have, in 
order to balance the same weight of cold air ; and as all rare- 



HEATING BY HOT WATER, HOT AIR, AND STEAM. 173 

bodies tend to rise vertically, in a dense medium, it follows, that 
when heated air enters a house by an aperture at one part of it, 
a very large portion of the heated air thus entering, must rise 
immediately towards the roof; and in practice we find this to be 
exactly the case. For, let any person examine the roof of 
a hot-house in a frosty night, heated by a hot-air stove, and he* 
will perceive the part immediately above the entrance of the 
air quite warm by the ascending heat, while all the rest of the 
roof may be covered with ice or snow. 

But the atmosphere of a house heated artifically, by whatever 
means, is always in motion ; with hot-water pipes it may be 
less perceptible, for the reasons already stated, but it is not 
the less real. The motion given to the atmosphere of a house 
depends upon the difference of temperature between the two 
bodies of air, externally and internally ; therefore a motion must 
continue in the air of a house artificially warmed, so long as the 
house requires warming, — that is, as long as any difference ex- 
ists between the internal and external atmospheres. 

Some advocates of hot-air heating found their arguments upon 
the fact that air can be raised to a higher temperature, in a 
given time, by a given amount of caloric, than water. This is 
probably true, if we calculate according to the bulk, without re- 
gard to the density, of the respective bodies ; but, supposing it to 
be true, then we know that, by the law already referred to, its 
rapidity in warming will just be i?i exact proportion to its rapid- 
ity in cooling, and vice versa. It is, therefore, manifest, that this 
property militates against it as an agent in heating horticultural 
buildings, as it is well known to be an all-important point, in 
warming these structures, to obtain an equilibrium of heat for 
the greatest length of time, and -with the least possible amount 
of attention, and experience has fully concluded that this is most 
effectually and most easily obtained by the circulation of hot 
water through wooden and metallic radiators and conductors. 

Suppose, for instance, that a house, containing 4000 cubic 
feet of air, is required to be heated, from 32° to 60°, and 
suppose the external thermometer to remain stationary at this 
point ; then, by calculation, we find that it requires double the 
amount of fuel to heat the atmosphere through the 28 degrees 



174 HEATING BY HOT WATER, HOT AIR, AND STEAM. 

between these two points, by means of water, that it does 
through the medium of air, i. e., by direct communication, in 
each case the calorific action being in pretty exact ratio to the 
combustion, and both acting under the most favorable circum- 
stances. This would, at first view, decide us in favor of hot 
air as a means of heating, in preference to hot water ; and the 
fact that the heat becomes more rapidly sensible by hot air, has 
induced many to come to a premature conclusion on this point. 

Let us, however, take another view of the position here 
alluded to, and consider the two methods in regard to their per- 
manency of heating power. We find also, by calculation, that 
while the temperature of the house is maintained at 60° for 
3-25 hours by hot air, with the same amount of combustion the 
temperature of 60° is maintained for 10 hours by hot water, or 
three times the period that the equilibrium is maintained by hot 
air. The same experiment shows that 2 bushels of coal will 
warm an equal volume of air in a hot-house the same length of 
time that 5-067 bushels will warm by direct connexion of its 
particles with the source of heat. 

Now, in a large house, or number of houses, this saving of 
fuel would, in a few years, amount to the difference of cost be- 
tween the two apparatuses, keeping out of the question the saving 
of labor, the cleanliness and neatness of the one compared with 
the other. In regard to these numbers, we may remark, that 
the calculations of some experienced and intelligent gardeners, 
drawn from accurate observation, have made the difference be- 
tween the two methods still greater, in regard to the consump- 
tion of fuel, — placing this position in still stronger light than by 
the calculation here given. 

This remarkable difference in the retention of heat is owing 
to the following causes. 

First. The power possessed by the water [as already ex- 
plained, see " Comparison of Water and Steam "] of absorbing 
and retaining a large amount of heat, and giving it off gradually, 
as the atmosphere requires it. 

Secondly. Owing to the body of metal with which the water 
is surrounded, which also absorbs and retains a large amount 



HEATING BY HOT WATER, HOT AIR, AND STEAM. 175 

of heat, and parts with it slowly to the air by which it is sur- 
rounded. 

Water is a better conductor of heat than air. Every gardener 
well knows how rapidly a wet mat, or any other wet substance, 
will carry off the heat in a frosty night, if laid over a hot-bed, 
or green-house. In fact, the temperature of a frame under such 
covering will fall quicker than if fully exposed. Yet the case 
is different if the mat be dry, because the apertures of the mat, 
and also the space between it and the glass, are filled with air 
at rest, — because the latter is a bad conductor of heat, and the 
former a good conductor. In a tank of water in a hot-house, 
the thermometer will indicate a temperature probably 10° above 
the atmosphere, while, by plunging the hand in the water, it will 
feel about 10° lower. This arises from the power possessed by 
the water of conducting the heat from the hand immersed in it. 
The effect in all these cases may appear different, but the prin- 
ciple of action is the same. Water conducts heat rapidly from 
a body warmer than itself, and conveys it to a colder one. 

Let a stream of air be forced through a tube 100 feet in 
length, entering at the temperature of 150°; by the time it has 
travelled, by its own specific gravity, to the end of the tube, 
it will be reduced to the temperature of the external atmosphere. 
A stream of water, under the same circumstances, will travel to 
the end of the tube with a very slight diminution of its tem- 
perature, probably only a few degrees, and will have heated the 
tube, if a good conductor, to nearly the same temperature as 
itself during its passage. 



SECTION IV. 

HOT-WATER BOILERS AND PIPES. 

1. Size of Boilers, and surface necessary to be exposed to the 
fire. — In adapting the boiler of a hot-water apparatus, it is not 
necessary, as in the case of steam boilers, to have its capacity 
exactly in proportion to the quantity of pipe that is attached to 
it. On the contrary, it is sometimes desirable to invert this 
order, and to attach a boiler of small capacity to a considerable 
length of pipe. We do not mean, however, in recommending a 
boiler of small capacity ■, to propose, also, that it should be of 
small superficies; for the efficiency of a boiler very much depends 
upon the quantity of surface exposed to the fire. The larger 
the surface exposed to the action of the calorific influence, the 
greater will be the economy of fuel, and, therefore, the greater 
will be the effect of the apparatus. 

In proposing the adoption of boilers of small capacity, how- 
ever, it is necessary to accompany the recommendation with a 
caution against running into extremes, for this error has been 
the cause of the inefficiency of apparatus in many instances. 
In some boilers, we have seen the space allowed for the water 
so very small that the boiler was thereby rendered completely 
useless. 

Too small a quantity of water, and too large a surface exposed 
to the fire, give rise to various evils, among which are the depo- 
sition of neutral salts and alkaline earths by the water which 
evaporates, contracting the water-way, and impeding circulation ; 
and also preventing the full action of the fire on the exposed 
surface of the boiler. 

But perhaps the greatest evil arising from this state of things, 
is from the repulsion of heat by the metal of the boiler. The 
quantity of water it contains being so small, and the heat of 
the fire very intense upon it, a repulsion is caused between 



HOT-WATER BOILERS AND PIPES. 177 

the iron and the water, and, consequently, the latter does not 
receive the full quantity of heat. The repulsion between heated 
metals and water has been ascertained to exist, even at low tem- 
peratures, being appreciably different at various temperatures 
below the boiling point of water. But as the temperature rises 
the repulsion increases with great rapidity; so that iron, when 
red-hot, completely repels water, scarcely communicating to it 
any heat, except, perhaps, when under considerable pressure. 

It is obvious that the extent of surface exposed to the fire 
should be in proportion to the amount of water contained in the 
boiler and the pipes ; and it is easy to estimate these relative 
proportions with sufficient accuracy, notwithstanding the various 
circumstances which modify the effect. Calculating the surface 
which a steam boiler exposes to the fire at 4 square feet for each 
cubic foot of water evaporated per hour, and calculating the 
latent heat of steam at 1000 degrees, we shall find that the same 
extent of boiler surface that would evaporate a cubic foot of 
water, of the temperature of 52°, into steam, of which the tension 
is equal to one atmosphere, would supply the requisite heat to 
232 feet of pipe, 4 inches diameter, when its temperature is to 
be kept at 140 degrees above that of the surrounding air. The 
following proportions for the surface which a boiler for a hot- 
water apparatus ought to expose to the action of the fire, will be 
found useful. 

Surface of boiler 
exposed to the fire. 4 inch pipe. 3 inch pipe. 2 inch pipe. 

3£ square feet will heat 200 feet, or 266 feet, or 400 feet. 
5£ " " " " 300 " 400 " 600 " 
7 " " " " 400 " 533 " 800 " 
8£ " " " " 500 " 666 " 1000 " 
12 " " " " 700 " 933 " 1400 " 
17 " " " " 1000 » 1333 " 2000 " 

A small apparatus ought, perhaps, to have rather more sur- 
face of boiler, in proportion to the length of pipe, than a larger 
one, as the fire is less intense, and acts with less advantage, than 
in large furnaces. It depends, however, upon a variety of cir- 
cumstances, whether it will be expedient to increase the quan- 
tity of pipe, in proportion to the surface of the boiler, beyond 



178 HOT-WATER BOILERS AND PIPES. 

what is here- stated ; for, although many causes tend to modify 
the effect, the above calculation will be found a good average 
proportion, under ordinary circumstances. The effect very much 
depends upon the quality of fuel, the force of draught, the con- 
struction of the furnace, &c, which, from what has been already 
said on these matters, will show that they will, in a great 
measure, influence the intensity of the heat received by the 
boiler. It is always safest, however, to work with a larger sur- 
face of boiler, at a moderate heat, than to keep the boiler work- 
ing at the maximum of its power. 

There is another cause, however, that will tend to modify the 
proportions which may be adopted. The data from which the 
calculation of the boiler surface is made assumes the difference 
to be 140° between the temperature of the pipe and the air with 
which it may be surrounded ; the pipe, in this calculation, being 
200°, and the air 60°. But if this difference of temperature be 
reduced, either by the air in the house being higher, or by the 
apparatus being worked below its maximum temperature, then, 
in either case, a given surface of boiler will suffice for a greater 
length of pipe. For, if the difference of temperature between 
the water and the air be only 120°, instead of 140°, the same 
surface of boiler will supply the requisite degree of heat to one 
sixth more pipe ; and if the difference be only 100°, it will sup- 
ply one third more pipe than the quantity stated in the table. 

It will, therefore, frequently occur, in practice, that the quan- 
tity of pipe, in proportion to a given surface of boiler, may be 
considerably increased beyond the amount which is given in the 
preceding table ; because, in forcing-houses, the temperature of 
the air may sometimes be above the number of degrees here 
given, and frequently the temperature of the water may be below 
100°, — the pipe not being required to be worked at its full heat; 
and, therefore, in both these cases, a larger proportion of pipe 
may be worked by a given sized boiler. 

In order to estimate the quantity of surface which is acted 
upon by the fire, an allowance must be made for the flues which 
circulate round the exterior of the boiler, (and all boilers should 
be so erected as to admit of the action of the heat round their 
sides.) Thus, suppose an arch boiler (Fig. 35) to be 30 inches 



HOT-WATER BOILERS AND PIPES. 

Fig. 35. 



179 




long, there will be about 8f square feet of surface exposed to the 
fire, that is, to its direct action underneath ; and suppose, also, 
that there are four external flues, one on each side, — or sup- 
posing that the flue went all round the boiler, top and all, — we 
may calculate that nearly one half of the effect is produced by 
these flues which would have been obtained had the direct action 
of the fire been employed on a like extent of surface ; therefore 
the flues will be equal to 5 square feet, making altogether 13£ 
square feet as the available heating surface of a boiler of this shape 
and size, which we consider far superior to the old form of boiler, 
as shown in the following cut, (Fig. 36.) A boiler of the size 

Fig. 36. 




here described (Fig. 35) would be sufficient to heat about 800 
feet of pipe, 4 inches diameter, when the excess of its tempera- 
ture above that of the surrounding air is 140°, as before stated ; 
a boiler of the same shape, 24 inches, has about 11 square feet 
of surface directly acted upon by the fire ; one 36 inches long 
has 16£ square feet of surface ; and one 42 inches long has 19 
square feet of surface ; the increase being directly proportioned 
in the simple ratio to the length. 



180 HOT-WATER BOILEES AND PIPES. 

A circular boiler, 30 inches diameter, with a 9 inch circular 
flue running round the outside, will expose nearly the same 
extent of surface to the fire as the one just described, (Fig. 35,) 
both being the same length, and therefore the one will be as 
effective as the other ; a slight diminution on the perpendicular 
length of the curve makes but little difference to its capacity for 
radiating caloric. 

The surfaces of any size of this shaped boiler can easily be 
calculated by the same rule ; but, instead of varying in the sim- 
ple ratio of the length or diameter, it will be found to be propor- 
tional to the square of the diameter, so that the proportion of 
surface increases more rapidly than in the arched boiler. Thus, 
a circular boiler, 24 inches diameter, has 8} square feet of sur- 
face exposed to the fire ; a 30 inch has 13f square feet ; a 36 
inch has 19| square feet ; and a 42 inch has 26f square feet 
exposed to the fire ; the small sizes having proportionally less 
surface, and the large sizes more than the high-arched boilers. 

The rules which are here given regarding boilers, are framed 
to suit common occurrence, and intended to guide practical men 
who have the management and working of common hot-water 
apparatus. There are some cases, however, where apparatus 
of great magnitude is necessary, in which these rules will not 
apply without modification. But as such instances are com- 
paratively rare, and, moreover, as no person that is a novice in 
the practical application of this principle of warming, will be 
likely to undertake, for his first essay, the responsible erection 
of an apparatus of great dimensions, it is the less necessary to 
enter at length into such cases as may be supposed to render 
any alterations of these principles necessary. 

It may, however, be observed, that cases may occur where a 
peculiar construction of apparatus may be desirable ; for instance, 
where, from a large quantity of required surface a furnace of 
very great power would be necessary ; and, in that case, a boiler 
which exposes a large surface, while it possesses but a small 
capacity, would obviously be injudicious, because the intense 
heat acting on a small body of water would probably generate 
steam to a high degree of elasticity in the boiler, and not only 



HOT-WATER BOILERS AND PIPES. 181 

produce much inconvenience, but neutralize the effects of what 
might otherwise be an efficient apparatus. 

The nearer the rules here laid down for regulating the size 
of boilers are acted upon, the more efficient will be the working 
of the apparatus. There is no advantage whatever gained by- 
using a larger boiler than is necessary to heat the pipes to their 
maximum temperature, — even though this temperature may 
never be required, — for, as the return-pipe should (if the appara- 
tus be working right) bring in a fresh supply as rapidly as the 
flow-pipe takes it away, the boiler is always kept full. It 
may be observed, that the circulation will be more rapid from a 
minimum boiler than from a maximum one, — that is, from a 
boiler whose capacity is rather below the proportion ; while a 
boiler whose capacity is above the proportion of the pipes, has a 
slower circulation ; and for all horticultural purposes, — though 
the former has some little advantage in the time of heating — 
the latter is decidedly to be preferred. 

In the following section, (Sect. V.,) further information will 
be found on boilers, etc., where different methods of heating, in 
practical operation, are figured and fully described. 

We may here state, in regard to the material for boilers for 
horticultural purposes, that cast-iron boilers, if properly made, 
will last much longer, and be also somewhat cheaper in the first 
instance, than malleable-iron ones, be the plates ever so good ; 
the principle of durability resting on the former not being 
injured by oxydation so much as the latter. In both cases, 
however, the durability depends very much on the kind of water 
used ; that least liable to form a deposition on the boiler being 
the best. 

2. Size and arrangement of hot-water pipes. — Some contro- 
versy has arisen, among engineers, gardeners, and others, respect- 
ing the size of tube most suitable for the purposes of heating 
hot-houses. 2, 3, 4, 5, and 6 inch pipes have been used, and 
experiments instituted respecting the merits of each ; from which 
it has been found that 4 inch pipes radiate more heat than any 
of the other sizes ; and, consequently, the 4 inch pipes are now 
most generally used. 



182 HOT-WATER BOILERS AND PIPES. 

The unequal rate of cooling of the various sizes of pipes, 
however, renders it necessary to consider the purpose to which 
they are applied. If it be desired that the heat shall be retained 
for a great many hours after the fire is extinguished, then pipes 
of larger dimensions must be used. Where a conservatory is 
very much exposed, and liable to fall below the minimum tem- 
perature during a cold night, then 5 inch pipe may be used, 
which will retain the heat longer than one of smaller size ; but a 
double length of pipe should always be used in doubtful cases. 
But, as a general rule, no pipe should be used of more than 4 
inches diameter, as the larger the pipe the greater the consump- 
tion of fuel, and more heat will be given out by 4 inch pipes, in 
proportion to the consumption of fuel, than by pipes of any 
other size. 

The ordinary method of arranging hot-water pipes is by 
placing the furnace and boiler at one end of the house, and lead- 
ing them along the front within a few inches of the wall. If 
the house be span-roofed, the pipes ought to travel completely 
round both sides; if single, or lean-to house, the pipe should 
pass along the front and return the same way; i. e., the flow and 
return pipes should be placed beside each other, as will be seen 
in the figures in the next section. The pipe ought never to run 
by the back wall of a house, except there be some reason to fear 
the entrance of frost in that quarter, which, in houses with thin 
walls, or those constructed with clapboards, is quite likely. In 
general cases, the heat rises with sufficient rapidity from the 
front, to prevent the entrance of frost at the back wall, unless it 
be near the bottom of the wall. 

In general, hot-water apparatus is so constructed that when 
the smoke leaves the boiler, it passes immediately up the chim- 
ney, by which an incredible amount of heat is lost. I have seen 
the thermometer rise to 200° when placed at top of a chimney 
of this kind, and an amount of heat thereby lost nearly equal 
to the whole amount radiated in the atmosphere of the house. 
This is the case with many heating apparatuses, without the 
smallest notice being taken of the fact. On making this remark, 
lately, to a most intelligent gardener, he doubted the fact of 
losing any heat by his chimney ; while, on trying the thermome- 



HOT- WATER BOILERS A2\D PIPES. 183 

ter at the top of his chimney, we found it rise in a few minutes 
to 137°, after having travelled through 20 feet of flue through 
the back wall of the house. 

Whatever apparatus be employed in heating a hot-house, the 
flue should always be taken advantage of. It must be remem- 
bered that smoke will not travel through a flue, — neither up 
nor down. — without first being rarefied by heat. The smoke, 
eadv described, is, in fact, a body of gases emitted from 
the fuel by the action of heat, and a portion of this it takes 
along with it on leaving the furnace. In its passage, it com- 
municates this heat to other bodies, as the flue ; and more s 
the flue is in a position more or less horizontal. A flue, there- 
fore, should, if possible, be carried the whole length before giving 
egpeas :: die smoke, by which a great amount of fuel may be 
economized. 

In laying down hot-water pipes, it is necessary to allow suffi- 
aeni room for their elongation and expansion when they become 
hot. "Want of attention to this has caused several accidents : a : 
the expansive power of iron, when heated, is so great, that 
scarcely anything can withstand it. The linear expansion of 
cast-iron, by raising its temperature from 32° to 212'. is •0011111. 
or about one nine hundredth part of its length, which is nearly 
equal to If inches in 100 feet. Therefore, it is necessary to 
leave the pipes unconfmed. so that they shall have freedom of 
motion lengthtravs : and, instead of con fin ing, as has frequently 
been done. :i::1:::t5 should be provided for their free expansion, 
by laying them on small rollers, or pieces of rod-iron, be: sea 
them and the bearers on which the"" nest ::r the contraction on 
coolins: is always e: : tc the expansion on heating, and unless 
-_.t can readily return to their original position when tbey 

me cool, the joints are apt to become loose and lea^:; : 
imimi all cast-iron pipes do, that are exposed to sudden 
mes of temperature. 

Z"rry hot-water apparatus should be provided with a supply- 
drteni i "ached to the boiler, or the pipes mc | pe riding 
from the supply-cistern should flow either into the return-pipe, 
or into the boiler, near the bottom. In no case atoakl it enter 
the flow-pipe, as it k more likely to emit vapor, and the sieam, 
16* $ 



184 HOT-WATER BOILERS AND PIFES. 

that may sometimes be generated on the surface of the water in 
the flow-pipe, would find egress, unless the supply-pipe were 
bent in the shape of an m to prevent it, which is a very good 
plan; and, as a small lead pipe of about l£ inch bore is suffi- 
cient to supply a boiler of considerable size, the pipe can easily 
be bent in any shape to answer the purpose. 

3. Impediments to circulation, fyc. The power which pro- 
duces the circulation of the water in the pipes is the specific 
gravities of the two bodies in the return and flow-pipes ; whether 
this force acts on a pipe 100 feet in length, or on one only 5 
feet in length, the result is precisely similar. 

Now it is evident that if this unequal pressure is the vis viva, 
or motive power, which sets in motion the whole quantity of 
water in the apparatus, in order to ascertain the exact amount 
of this force, it is only necessary that we know the specific 
gravities of the two columns of water, and the difference will, of 
course, be the effective pressure, or motive power. This can be 
accurately determined when the respective temperatures of the 
water in the boiler and in the descending or returning pipe are 
known. 

As this difference of temperature rarely exceeds a very few 
degrees in ordinary cases, the difference of the weight of the two 
columns must be very small. But, probably, the very trifling 
difference that exists between them, or, in other words, the 
extreme smallness of the motive power, is very imperfectly com- 
prehended, and will, perhaps, be regarded with some surprise, 
when its amount is shown by exact computation. 

In order to ascertain, without a long and troublesome calcula- 
tion, what is the amount of motive power for any particular 
apparatus, the following table has been constructed. An appara- 
tus is assumed to be at work, having the temperature in the 
descending pipe 170°, and the difference of pressure upon the 
return-pipe is calculated, supposing the water in the boiler to 
exceed this temperature, by from one to twenty degrees. This 
latter amount will exceed the difference that usually occurs in 
practice. 

By referring to the annexed table, it will be found that when 



HOT-WATER BOILERS AND PIPES. 



185 



=M 



PJ 



the difference between the temperature of the flowing 
returning columns is 8 degrees, the difference in weight is 
grams on each square inch of the section of the return- 
supposing the height of the boiler A (Fig. 36, 
B) to be 12 inches. This height, however, is 
only taken as a convenient standard' from 
which to calculate ; for, probably, the height 
may, in many instances, be more than this, 
though it will seldom be less. 

Now, suppose that, instead of 12, 18 
inches was the distance between the two 
pipes, that is, between the top of the upper 
and the centre of the lower pipe, and the 
pipe 4 inches in diameter ; if the difference of 
temperature between the water in the boiler 
and the return-pipe be 8 degrees, the pressure 
on the return-pipe will be 153 grains, or 
about one third part of an ounce ; and this 
will constitute the whole amount of motive 
power of the apparatus, whatever be the 
length of pipe attached to it. If such an 
apparatus have 100 yards of pipe 4 inches in 
diameter, and the boiler contains, say, 30 gal- 
lons of water, there will be in all 190 gallons, 
or 1900 lbs. weight of water, kept in continual 
motion by a force equal only to one third of 
an ounce. This calculation of the motive 
power will vary under different circumstances ; 
and, in all cases, the velocity of the circula- 
tion will vary simultaneously with it. 



and 
8-16 

pipe, 



9 



GO 



186 



HOT-WATER BOILERS AND PIPES. 



Difference in weight of two columns of water each one foot high, at various 
temperatures. 



Difference in 














temp, of the 


Difference 


in weight, of two columns of water contained 


Difference of 


two columns 
of water in 




in 


different pipes. 




a column one 
foot high. 


degrees of 
Fah.'s scale. 














1 in. diam. 


2 in. diam. 


3 in. diam. 


4 in. diam. 


5 in. diam. 


per sq. inch. 




grs. weight 


grs. weight 


grs. weight 


grs. weight 


grs. weight 


grs. weight 


2° 


1-5 


6-3 


14-3 


25-4 


33-6 


2.028 


4° 


3-1 


12-7 


28-8 


51-1 


110-1 


4-068 


6° 


4-7 


19-1 


43-3 


76-7 


211-7 


6-108 


8° 


6-4 


25-6 


57-9 


120-5 


250-0 


8-160 


10° 


8-0 


32-0 


72-3 


128-1 


317-5 


10-200 


12° 


9-6 


38-5 


87-0 


154-1 


376-1 


12-264 


14° 


11-2 


45-0 


101-7 


180-1 


390-9 


14-328 


16° 


12-8 


51-4 


116-3 


205-9 


449-1 


16-392 


18° 


14-4 


57-9 


1310 


231-9 


5220 


18-456 


20° 


16-1 


64-5 


145-7 


258-0 


700-0 


20-532 



The above table has been calculated by the formula given 
with table IV., (see Appendix,) for ascertaining the specific grav- 
ity of water at different temperatures. The assumed tempera- 
ture is from 170° to 190°. 

It will be observed, in the foregoing table, that the amount 
of motive power increases with the size of the pipe ; for instance, 
the power is four times as great in one of 4 inches diameter as 
in one of 2 inches, and nearly six times as great in one of 5 
inches. The power, however, bears exactly the same relative 
proportion to the resistance, or weight of water to be put in 
motion, in all the sizes alike ; for, although the motive power is 
four times as great in pipes of 4 inches as in those of 2 inches, 
the former contains four times as much water as the latter. 
The power and the resistance are, therefore, relatively the same. 

These calculations are given with the view of showing how 
trifling a cause may impede the proper circulation of the hot 
water in pipes, and that, when once obstructed, how impossible 
it is for an apparatus to work. Trifling as this power may 
appear, yet upon its action depends entirely the efficiency of an 
apparatus. Seeing that the motive power is so small, it is not 
surprising that, by an injudicious arrangement of its parts, the 
motion may frequently be impeded and even destroyed ; for the 
slower the circulation of the water, the more likely is it to be 
interrupted in its course. 



HOT-WATER BOILERS AND PIPES. 187 

There are two ways by which the motive power may be 
increased. One, to allow the water to cool a greater number of 
degrees between the time of its leaving the boiler and the period 
of its return through the descending pipe. The other, by 
increasing the vertical height of the ascending and descending 
columns. The effects produced by these two methods are pre- 
cisely similar; for, by doubling the difference of temperature 
between the flow and return pipes, the same increase of power 
is obtained as by increasing the vertical height. 

There are two methods of increasing the difference of temper- 
ature between the flowing and returning pipes. First, by 
increasing the quantity of the pipe, so as to allow the water to 
flow a greater distance before it returns to the boiler. Secondly, 
by diminishing the diameter of the pipe, so as to expose more 
surface in proportion to the quantity of water contained in it, 
and by this means to make it part with more heat in a given 
time. 

The first of these methods, although the most practical, is 
ncessarily limited, in some instances, to the length of the build- 
ing to be heated, to which the length of pipe must be adjusted, 
in order to obtain the required temperature ; and, as to the 
second, we have already enumerated many objections against 
the use of small pipes. Where the motive power, therefore, is 
not of sufficient strength, the increase of the height of the col- 
umn ascending from the boiler must be depended on for an 
additional motive power. 

In all cases, the rapidity of circulation is proportional to the 
motive power, and, in fact, it is the index and measure of its 
amount. For, if, while the resistance remains uniform, the 
motive power be increased in any manner, or in any degree, 
the rapidity of circulation will increase in a relative proportion. 

Now, the motive power may be augmented, as we have seen, 
either by increasing the vertical height of the pipe, by reducing 
its diameter, or by increasing its length. If, by any of these 
means, the circulation be doubled in velocity, then, as the water 
will pass through the same length of pipe it did before, in one 
half the time, it will only lose half as much heat as in the for- 
mer case, because the rate of cooling is not proportional to the 



188 HOT-WATER BOILERS AND PIPES. 

distance through which the water circulates, but to the time of 
transit. If, then, by raising the pipes vertically, the difference 
between the temperature of the flow and return pipes be in- 
creased, it appears to be the most practical method of increasing 
the velocity of motion. The increased velocity, therefore, is 
indicative of increased power, and in a hot-water apparatus it is 
the velocity of circulation which enables it to overcome any 
extraordinary obstructions. 

Neither the principle nor the practice of an apparatus is in 
the least affected by having an additional number of pipes lead- 
ing out of, or into, the boiler ; the effect is the same, whether 
there be more flows than return pipes, or, conversely, more return 
than flow pipes. 

4. Level of Pipes. — Some persons have supposed that if the 
pipes be inclined so as to allow a gradual fall to the boiler in its 
return, additional power is gained. This appears very plausible, 
particularly with regard to some forms of apparatus, but the 
principle is entirely erroneous. This error appears to arise from 
treating the subject as a simple question of hydraulics, instead 
of a compound result of hydrodynamics. If the question were 
only as regards a fluid of uniform temperature, then the greatest 
effect would be obtained by using an inclined pipe ; but the 
water in the pipes we are now treating of, is of varying density 
and temperature, which very materially alters the results. 

Contrary to the ideas of some persons, the circulation of the 
water first takes place in the lower pipe ; in consequence of the 
water in the boiler becoming lighter by the absorption of heat, 
the column of water in the return-pipe, being of greater density, 
forces its way into the boiler, when the water in the upper pipe 
falls into its place. Now, suppose the distance between the 
entrance of the return-pipe and that of the flow-pipe be 12 inches. 
This distance is neither increased nor diminished by any incli- 
nation of the return-pipe towards the boiler, the effective pressure 
being in both cases the same. 

Discarding the erroneous hypothesis that the motion of the 
water commences in the upper pipe instead of the lower one, — 
and the motion commences at the entrance of the lower pipe into 



HOT-WATER BOILERS AND PIPES. 189 

the boiler, which we have frequently proved, — it is, therefore, 
evident that there can be no advantage by making the pipe to 
incline from the horizontal level ; for whether the water descends 
through a vertical or through an inclined tube, the force of 
gravity will only be equal to the perpendicular height ; there 
must, therefore, be an equality of pressure on the boiler under 
all circumstances, whether the pipe entering the boiler be on a 
level, or inclined from its junction with the flow-pipe. 

When it is necessary to sink the return-pipe below the level 
of the boiler, there must be a sufficient weight of water in the 
pipes, above its level, to overcome the perpendicular column that 
exists below the level of the boiler, otherwise the tendency of 
the lower column will be to a retrograde motion. The only way 
is to raise the pipe sufficiently to afford a perpendicular return- 
ing column of sufficient pressure to raise the water in the per- 
pendicular pipe attached to the boiler. 

If the flow-pipe be carried on a horizontal level with the boiler, 
and the return-pipe carried below the level of the boiler, it is 
scarcely possible to obtain any circulation ; and if this depth be 
much, no circulation at all can be obtained. We have seen some 
costly apparatuses completely useless on this account ; and those 
erectors of heating apparatus, unacquainted with the principles 
of hydrodynamics, are very apt to commit similar mistakes. 
The velocity of circulation in such apparatus will be just in 
proportion to the difference of weight between the columns 
above and below the boiler. . 

It must not be supposed that water will not circulate in pipes 
below the level of the boiler ; and much trouble and expense 
have frequently been incurred in consequence of being ignorant 
of this position. All that is necessary is to give the upper section 
of pipe a sufficient preponderance to raise the water in the lower 
one, allowing for the superior density of the water in the lower 
pipe. It, however, requires considerable judgment in adopting 
any such forms of apparatus as this, for many concurring cir- 
cumstances are essential to complete success. It should, there- 
fore, never be adopted when a common horizontal working 
apparatus can be introduced. 



190 HOT-WATER BOILERS AND PIPES. 

5. Accumulation of air in pipes. — It is necessary to make 
provision for the escape of air in the pipes, which sometimes so 
accumulates as to prevent circulation. This is more especially 
the case when the apparatus is complicated, and has many turn- 
ings and vertical bends in the pipes. It generally collects at the 
upper bends of the pipe, but this will depend very much upon 
the mode of supplying the apparatus with water. It frequently 
requires the greatest care and the closest attention to discover 
where the air is likely to lodge, as the most trifling alteration 
in the position of the pipes will entirely alter the arrangements 
in regard to the air-vents. Want of attention to this has been 
the cause of many failures, and the discovery of the places 
where the air accumulates is sometimes a matter of difficulty. 
For although it be true, in a general sense, that air will rise to 
the highest part of the apparatus, it will frequently be prevented 
from getting to the highest part by alterations in the level of 
the pipes, and by other causes. 

As water, while boiling, always evolves air, it is not sufficient 
merely to discharge the air from the pipes on first filling them, 
because it always accumulates ; and, in many instances, it is 
desirable to have the air-vent self-acting, either by using a valve, 
or small open pipe ; but we have generally found a cock most 
convenient. 

The size of the vent is not material, as a very small opening 
will be sufficient to allow the escape of air. The rapidity of 
motion in fluids is inversely proportional to their specific gravi- 
ties, as water is 827 times more dense than air ; an aperture 
which is sufficiently large to empty a pipe in 14 minutes, if it 
contained water, would empty it, if it contained air, in one 
second. Air being so much lighter than water, it is of course 
necessary that the vents provided for its escape should be placed 
at the highest parts of the apparatus, for there it will always 
lodge when no impediment occurs to prevent it; but it will 
sometimes be found necessary to have several in different parts 
of the apparatus. 

Though it is perfectly easy to provide for the discharge of the 
air from the pipes, — as far as the mere mechanical operation is 
concerned, — ■ it requires much consideration and careful study to 



HOT-WATER BOILERS AND PIPES. 191 

direct the application of those mechanical means to the exact 
spot where they will be useful. We have frequently seen 
mechanics, who, though well acquainted with the practical 
details of the apparatus they were erecting-, yet were perfectly 
ignorant of the principles on which it works ; hence the success 
of such an apparatus must be entirely a matter of chance. 
Wherever alterations of the level occur, vents should be pro- 
vided for the escape of air ; and, as we have said, a small tap 
(or cock) will be the most convenient method of outlet. 

In a complicated arrangement of hot-water apparatus, it is 
sometimes so very difficult to detect the various causes of inter- 
ference, and the impediments which arise are often so apparently 
insignificant in their extent, that when ascertained they are 
frequently neglected. Those, however, who bear in mind how 
very small is the amount of motive power in any apparatus of 
this description, will not consider as unimportant any impedi- 
ment, however small, which they may detect ; moreover, they 
will immediately see the propriety of having the evil in ques- 
tion put right. But, in the more complicated forms of the 
apparatus, so many causes become operative in impeding the 
circulation, that the real cause of impediment may elude the 
detection of even an experienced practitioner. 

We will now proceed to give a description, in detail, of various 
methods of heating, which come within the range of our own 
experience, accompanying the descriptions with sketches, by 
which their details will be more easily understood. 
17 



SECTION V. 

VARIOUS METHODS OF HEATING DESCRIBED IN 
DETAIL. 

The heating- of hot-houses, by any of the ordinary methods 
of warming these structures, has hitherto been attended with 
extravagant expense. The difficulty of obtaining, at a reason- 
able price, the means of keeping up the desired temperature, 
during long and severe winters, — the expense of the apparatus, 
— the annual cost of repairs, — the continual outlay for fuel, — 
together with the incidental expenses and trouble of working 
them, has, in many instances, proved a barrier to their erection, 
and has induced many to abandon the attempt, who had well 
nigh carried it into execution. Many lovers of exotic gardening 
have thus been diverted from the enjoyment of this pleasant and 
healthful pursuit; and hence it is of the utmost importance, 
especially to amateurs and others having small establishments, 
and who do not keep a regular gardener, that the internal ar- 
rangements of a plant-house, and, above all, the heating arrange- 
ments, should be so constructed as to be dependent upon the 
very smallest possible amount of time and attention, and likely 
to produce the least injury by neglect. 

Among the numerous systems of heating lately applied to 
horticultural buildings in England, is one called Polmaise, from 
its having originated at a place in Scotland of that name, — the 
seat of the late Mr. Murray, near Sterling. The principles 
upon which this method is founded are not new, and the system 
itself, in other modifications, dates from a period much more 
remote than any other with which we are acquainted. This 
system is applied, in a more practical and perfect form, to the 
warming of many public and private buildings in this country. 
The very general adoption, however, of this system, does not, in 
the smallest degree, give us a warrant against its defects. It 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 193 

has been ascertained that air heated to a temperature of 300 de- 
grees, becomes so deprived of its organic matter, and otherwise 
changed in its properties, as to be unfit for the sustenance of 
either animal or vegetable life, in a state of healthy and vigorous 
development, for any length of time ; and hence the admission 
of a current of highly heated air into a dwelling room, or into 
a well glazed hot-house, if no means are taken to restore its 
original properties, must, in a short time, become sensibly in- 
jurious to the animals and vegetables that are compelled to 
breathe it. 

And this we find to be practically the case. Every gardener, 
on entering a hot-house so heated, is immediately sensible of 
the presence of contaminating gases in the atmosphere, whether 
arising from the combustion of fuel, or otherwise, and he is too 
w T ell acquainted with its effects on vegetative beings to allow 
his tender plants to absorb it ; hence he takes immediate meas- 
ures of modifying what he cannot possibly prevent. It can 
scarcely be doubted, that a vast amount of sickness and diseases 
of the respiratory organs is, in a great measure, attributable to 
the same circumstance, especially in people of sedentary habits, 
who confine themselves to close chambers, warmed by currents 
of hot air, or highly heated stoves. The latter, in this respect, 
is probably worse than the former ; for, in the one, the supply of 
air to be heated is drawn from the external atmosphere, and, 
consequently, is less likely to contaminate the air of the room, 
although, when conducted into the room at high temperatures, 
the atmosphere of the latter, without egress as well as ingress 
of air, must ultimately become so. In the case of stoves, how- 
ever, it is different, for by them the same atmosphere is heated 
over and over again, by convection. The particles of air in 
contact with the stove first become heated, these expand with 
the heat, and, consequently, becoming lighter, rise, and the 
colder particles supply their place, which also expand, rise, and 
are in their turn replaced by others. Here the supply of air to 
be warmed is drawn directly from the room itself; thus com- 
pelling the inmates to inhale the same contaminated atmos- 
phere for days together, without mixture or admission of fresh 
air, except the small portion that finds an unwelcome entrance 



194 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

by the occasional opening of the door ; and in the severe weather 
of our winters, with the thermometer below zero, this portion is 
frequently small indeed. The pleasure and ability of exercising 
our physical functions in cold weather, will be in exact propor- 
tion to the frequency of practice ; and it is truly surprising, that 
with so much positive proof of direct injury resulting from con- 
tinued confinement over highly heated stoves, many will, never- 
theless, persist in so pernicious a custom, — a custom which is 
truly national, and which renders the influence of these stoves 
as baneful as that of the Upas tree, and sends thousands an- 
nually to an untimely and premature grave. 

I have observed, by some articles that have lately appeared in 
an excellent horticultural periodical, (Downing's Horticulturist,) 
that this much talked of system of warming horticultural struc- 
tures with hot air, called Polmaise, has been adopted by some 
individuals in this country. These individuals have been misled 
by the extravagant statements, or rather mis-statements, that 
have from time to time appeared in the Gardener's Chronicle, 
(of England,) by its talented editor and others under his influ- 
ence. Those who have been in the habit of reading that paper 
in this country, and noticed the laudatory articles that have so 
frequently appeared in it, in favor of this method, yet unac- 
quainted with the practical opposition it has received by num- 
bers of experienced men, in every way qualified to decide upon 
its merits, can scarcely be blamed for adopting a system said to 
possess so many advantages over all others ; and when it is con- 
sidered that the gardening journal, which represents the opinions 
of practical men in that country, is but little read in America, — 
in fact, I may say, almost unknown, save by a few individuals, — 
it is not surprising that they should have been betrayed into the 
system supported by such authority. It is difficult, indeed, to 
account for the strong-headed and one-sided policy of the advo- 
cates and promoters of Polmaise. The fact is well known, that 
the system, and the defects connected with it, were thoroughly 
established many years before it was applied at the place from 
which it takes its name. In many places it had been tried, and 
found inferior, and far more fickle than the common smokf 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 195 

flue.^ It originated at Polmaise Gardens, from the following 
circumstances : — A church in the neighborhood of that place 
had been warmed by a hot-air furnace, similar to those ,used in 
dwelling-houses in this country. A gardener at that place 
examined it, and thought it a good plan to warm his hot-houses ; 
accordingly, he applied something of the same kind to heat his 
vinery. The thing was entirely new to the worthy gardener, 
as well as to his employer, who sent an account of it to Dr. 
Lindley, of the Gardener's Chronicle, who forthwith espoused 
the system, extolled it to the skies, and induced various individ- 
uals to adopt it ; and those who would not, he straightway de- 
nounced as interested and dishonest men. The gardening com- 
munity arose in arms, and waged war against their theoretical 
foes, until its so-called originators were confounded at the amount 
of opposition excited. No controversy connected with gardening 
was ever carried on with so much virulence as this one on Pol- 
maise heating ; and no system has been so severely tested, to 

* The premature encomiums so liberally lavished upon this system, by 
the zeal of its promoters, have neither shamed imposture nor reclaimed 
credulity. Deceptions seldom stand long against accurate experiments, 
and the mere charm of novelty soon vanishes, when economy and util- 
ity are both against it. The desire of notoriety, if nothing else, has too 
often induced parties to impose on the credulity of those who have not 
science enough to investigate its principles, nor practice enough to dis- 
cover its defects. Nothing can more plainly show the necessity of doing 
something, and the difficulty of finding something to do, to obtain these 
paltry ends, than the getting up of this method of heating hot-houses ; 
and this, too, by those who know, or ought to know, better, and who 
ought to have rejected it with contempt. When a system has no intrin- 
sic value, it must necessarily owe its attractions to theoretical embellish- 
ment, and catch at all advantages which the art of writing can supply. 
Trifles always require exuberance of ornament ; the building which has 
no strength or utility, can be valued only for the novelty of its charac- 
ter, or the money which it cost. It is certain that the advocate of a 
new system is less satisfied by its failure, than its success, even when 
no part of its failure can be imputed to himself, and when the fruits of 
his labor are tested by those who can discover their real worth. No 
man has a right, in things admitting of gradation, to throw the whole 
odium upon his opponents, and totally to exclude investigation and in- 
quiry, by a haughty consciousness of his own excellence. 



196 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

prove its worth. Gardeners, amateurs, and all, entered the arena 
of experiment and discussion. Still its promoters would not 
flinch from their original position, and, right or wrong, would 
cram it down gardeners' throats, whether it was digestible or 
not; and that, too, without one tittle of evidence in favor of it, 
except ripe grapes in September, — a period when grapes would 
ripen themselves, without any artificial heat at all. Yet its 
cheapness and simplicity were its recommendation, and for 
some successive winters many went to work Polmaising their 
hot-houses, tearing down their furnaces, flues, &c, and con- 
verting them into Polmaise stoves, hot-air drains, and other 
appurtenances of Polmaise ; but, after a short trial, and a good 
deal of plant-killing, they one and all abandoned the sys- 
tem with disgust. Still, amidst all this dust and dirt, and 
smoke and gas, created by the cracking of plates and the 
breaking of tiles, the Doctor maintained his ground, until, like 
the conquered hero, he was left alone in his glory, in the 
midst of the wreck and ruin he had created. What seems very 
strange, he never erected one, or caused one to be erected, at 
the Horticultural Society's garden, where he had unlimited con- 
trol, and ample opportunity of so doing ; and those who erected 
them by his recommendation and advice, were obliged to ac- 
knowledge them unqualified failures, notwithstanding all their 
alterations and improvements upon the original plan, which was 
simply this : — A hot-air furnace is placed behind the back wall, 
about the centre of the house ; immediately opposite the stove 
there is an aperture in the wall, for the admission of the heated 
air into the house ; directly in front and above this aperture, a 
woollen cloth is suspended, which is kept constantly moist by a 
number of worsted skeins depending from a small gutter, fixed 
on a frame of wood, which supports both the gutter and the 
cloth, the lower end of the latter reaching the ground. The 
cloth is made thicker in the middle, in order to equalize the 
heat, — an arrangement which is absolutely necessary ; for if the 
cloth was an equal thickness all over, the centre of the house 
would be heated to a scorching degree, (by the rush of hot air,) 
while the ends would be comparatively cold. By means of 
drains under the floor, the fire-place is supplied with air from 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 197 



Fig. 37. 




198 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



inside the house, part of which is used for the combustion of 
fuel ; the rest passes over the heated stove and enters the house 
through the apertures above noticed. 

Fig. 38. 




Such is the original system of Polmaise heating, which has 
created so much sensation in England, but which is now aban- 
doned for some one or other of the many improved methods to 
which it gave rise, the most perfect and scientific of which, I 
have represented in the accompanying cuts, Figs. 37, 38, and 39. 
The arrows marked a, in the three figures, show the entrance of 
the cold air from the external atmosphere ; and its passage to 
the fire-place, beneath the floor of the house, is further shown 
by the arrows b, in Figs. 37, 38, and 39. Its passage over the 
hot plate, through the chamber, under the bed, and thence into 
the house, is marked by c, attached to each arrow in the three 
figures ; d, the fire-place ; e, a tank containing water, imme- 
diately over the cast-iron plate ; f, a small funnel, or tube, for 
supplying water to the tank ; g, (Fig. 38,) shows the bed on 
which the plants are placed, resting on cross-bars, and filled 
with pieces of brick, having a layer of sand or sawdust on top ; 
this can be converted into a stage, if desired. This is Mr. 
Meek's modification of Polmaise, from whom the drawing ap- 
peared in the Gardener's Chronicle, and was there represented 
as something very near perfection in heating, if not perfection 
itself. The above sketch is somewhat altered and simplified in 



VARIOUS METHODS OF HEATEXG DESCRIBED IN DETAIL. 199 




D 



the formation of the drains; and yet, 
in all conscience, it is complex and 
compound enough for a heating appa- 
ratus, as any person can see by a glance 
at the above sketches. It is difficult toe 
discover wherein lies its superiority 
over the old smoke-flue, and it is 
clearly evident, that it has neither 
cheapness, simplicity, nor economy in 
fuel, to recommend it; and, as to its 
working, it is infinitely more precarious 
than the common flue, and the loss of 
heat is certainly much greater. This 
loss has been stated, by those who have 
tested its merits, to be at least one 
fourth of its whole heating power. Air. 
Ayres, one of the most enlightened 
gardeners in England, stated, in a paper 
on that subject, published in the Gar- 
dener's Journal of 1847, that Mr. Meek 
wasted more heat from his one house, 
than he (Mr. Ayres) did from one fire 
that had nine different arrangements to 
work ; and in a Polmaise apparatus that 
Mr. Ayres had erected, the waste of 
heat was enormous ; that in ten min- 
utes after the fire was lighted, he could 
ignite a piece of paper at the top of the 
chimney with the greatest ease ; and 
when the same gentleman asked one 
of its strongest advocates the following 
question, " If you had a range of houses 
to ' heat in the best possible manner, 
would you abandon hot water for Pol- | 

maise ? " he was answered, " No, cer- 
tainly not." 

I have quoted the opinion of Mr. Ayres, because he is well 
known to be one of the best authorities on matters of practical 



□ 



□ 




200 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

importance, connected with horticulture, at the present day, and 
his opinions are endorsed by almost every gardener of note in 
England. Mr. Fleming, of Trentham, and Mr. Paxton, of 
Chatsworth, as well as many others, regarded it as a thing ut- 
terly unworthy of notice. Mr. Ayres, in the same paper already 
quoted, puts to the advocates of Polmaise the following conclu- 
sive and unanswerable query. If Dr. Lindley, or any other of 
its advocates, can point to one place where the apparatus is at 
work, and as efficacious as a hot-water apparatus ; if they can 
refer us to any one place, where we can see better productions 
than what have resulted from the use of hot water, why, says 
he, I am ready to spend five sovereigns to go to see it, and be 
convinced of my error in opposing it ; but until then, it is mere 
nonsense to suppose that any responsible person will adopt it. 

As an example of a combination of hot water and hot air, 
applied in a practical and scientific manner, the following sys- 
tem is superior to any other with which I am acquainted, espec- 
ially for small houses. It supplies heat, moisture and air, either 
singly or combined. It consists of a cast or plate iron boiler, a, 
for containing the water ; in shape it is not unlike a pretty large 
inverted flower-pot, with a hollow between its sides, about four 
or five inches wide, having one pipe entering near the top for 
the flow, and another at the bottom for the return, with a tube 
entering quite through to the fire-chamber, as represented at b, 
c, and d ; then there is a hot-air chamber round the boiler and 
fire-place, as shown at e, e, e, Figs. A, B, and C ; the boiler 
rests on a circular course of bricks, forming the furnace/,/, 
Figs. B and C. The whole is enclosed by the hot-air chamber, 
from which the air is conducted into the house, at k, and is 
supplied with cold air, both for the combustion of fuel, and 
drawing off the heated air, at i, i, Fig. C. The fire is fed 
through the door in the chamber, j, opposite which is a smaller 
door in the furnace, at k. In Fig. C is shown the door of the 
ash-pit, I, through which the ashes are drawn. We know of no 
apparatus, where a small green-house or conservatory is required 
to be heated, that will do it so effectually and economically as 
this. No particle of heat generated is lost, and in its simplicity 
is everything that a novice could desire. Here is nothing more 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 201 



Fig. 40. 




202 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

than a cone of cast or plate iron, with hollow sides, one hole 
for a flow, and one for a return pipe, (these pipes can branch 
into several directions, if necessary, on leaving the boiler,) and 
a channel through it, with a flange, or neck, on which to fix the 
smoke pipe ; build the boiler, thus formed, on a fire-place, with 
just distance sufficient below the edge of the cone for a door, to 
supply fuel ; this door should be quite narrow, in order to let 
the edge of the boiler as far down as possible. The hot-air 
chamber should be built of brick, and, if exposed to the atmos- 
phere, should be at least one foot thick. In fact, the thicker 
the wall of the hot-air chamber is made, the better will the 
heat be retained. A tank of water is placed over the hot-air 
entrance, inside the house, for evaporation. If this system be 
not bungled in the construction, it will be found as cheap as 
any other, and the expenditure for fuel is but trifling. The cir- 
culation of the water is complete, and the air in the chamber is 
neither roasted nor burned, as it is chiefly received through the 
boiler, and, consequently, is possessed of more natural purity, 
which is so essential to vegetable life ; and it requires so little 
attention that any amateur can manage it without much trouble. 
Even in pretty severe weather, when set fairly agoing in the 
evening, it wants no more attention till morning ; set it right in 
the morning, and you may safely leave it again till night. Nor 
is it liable to accident or derangement. Not the least of its 
recommendations is its economy of fuel, — a circumstance of con- 
siderable importance, especially where the cost of fuel is high ; 
and, therefore, the economy thereof is of double moment to the 
proprietor. 

We have never seen this system applied to large structures, but 
we have no doubt, were the apparatus made in proportion to its 
work, it would answer as well in large as in small houses ; at 
all events, there is no reason why furnaces and boilers of every 
description should not be chambered round in a similar way ; 
a very great amount of heat, that is now lost, would be turned to 
advantage, and I think it is not too much to say, that hot-houses 
could be heated at one half the expenditure of fuel. 

The system of heating two, three, or more, houses with one 
boiler, is one of those valuable improvements which science, 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 203 

combined with mechanical ingenuity has devised, and which 
has been carried out in practice with the most gratifying 
success, — so much so, that in some places, separate apparatuses 
have been torn down, and this system adopted instead, merely 
on account of the fuel economized thereby. Among the many 
systems brought before the public, under the fine-sounding name 
of improved, it is doubtful whether any of them have given so 
entire satisfaction as the above, where it has been properly con- 
structed. The facility so admirably afforded by this method of 
heating any of the connected houses in the space of a few min- 
utes after it is found necessary, is certainly a great recommen- 
dation in its favor. In short, you have only to turn a tap, and 
the thing is accomplished. Fig. 41 -'^presents the ground plan 
of four houses heated in this way, and most efficiently. 

It will be seen from the plan, that the two end houses on the 
front are heated by the pipes flowing and returning into the 
pipes which supply the hot water for the two houses standing on 
the back. This is easily accomplished by having a tap on each 
pipe where it enters the house, so that either house may be 
heated, or both together, if required. 

In the extensive forcing-establishment of Mr. Wilmot, at Isle- 
worth, near London, no less than seven ranges of houses, each 
ninety feet in length, are heated by one boiler, and all are heated 
effectually, and that too for the purpose of forcing grape-vines. 
In many other places, in England, we know that this method 
has been adopted with the very best results. 

In the plan here given, the box, (Fig. 42,) which is given on a 
larger scale, is situated immediately over the boiler. It may, 
however, be on the same level, or nearly so, and situated in any 
corner out of the way. The boiler here used is a common saddle 
boiler, and with a large apparatus, is probably the best boiler 
for general purposes. The apartments, g g, in the cut (Fig. 41) 
are offices for the garden, tool-house, potting-room, fruit-room, 
&c, and may be used as a mushroom-house. As the hot-water 
pipes pass through them, they are kept slightly warmed, and 
may be made useful as store-rooms and other kinds of garden 
offices. 

In some places in England, no less than eight or ten different 
18 



204 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 




*m 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 205 
Fig. 42. 




departments are heated by one boiler ; some of them going at 
one time, and some at another, and sometimes all going together, 
and each having abundance of heat.* The convenience of this 
system cannot be too highly appreciated, especially when there 
are a number of small plant-houses situated near each other. 
For instance, suppose the boiler to be at work for one of the 
houses, which may be a plant-stove or forcing-house ; well, you 



Fig. B. 




# Fig. B shows the common method of placing supply-cisterns. They 
may be placed in some convenient situation and attached by a small 
pipe to the apparatus. To prevent the escape of vapor, it is desirable 
to bend the pipe into the form shown at a b, as the water in the part of 
the inverted syphon at a, will remain quite cold. 



206 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

go out before bed-time, and find the sky clear and frosty, con- 
trary to your anticipations in the early part of the evening, — 
and how often do we find this really to be the case, — you enter 
into your green-house, and you find the thermometer travelling 
down rather quickly towards the freezing-point. Kindling fires 
is generally an unpleasant business at this time of night, and 
we are pretty often inclined to let the plants take their chance, 
rather than be at the trouble of doing it, even if it should cost 
us half a night's sleep through anxiety. Here, this unpleasant 
business is dispensed with, and the anxiety too, as well as the 
sitting up till the house is heated and safe for the night. You 
go to the tank or box, which is generally situated so as to be 
easily got at, in a recess made in the wall, perhaps, or immedi- 
ately over the boiler, as represented in Fig. A ; but, in any case, 
it should be so arranged as to be always of easy access from the 
houses. The arrangement of the pipes makes no difference, 
providing the accumulating tank be sufficiently elevated. The 
moment the water is put on, the circulation commences ; in 
flows a delightful stream of hot water, warming the pipes as it 
proceeds through the flow and return; a vivifying glow of 
warmth pervades the chilly atmosphere of your green-house, and 
you can retire to rest without being troubled with anxious 
thoughts about your plants, let the weather turn as it may. 

It may appear, that, by this arrangement, a larger quantity of 
fuel will be required for a single house, than if that house had 
an apparatus for itself. Not so, however ; for, by close observa- 
tion, it is found that the consumption of fuel is pretty nearly in 
proportion to the water heated, and that the heat given off by 
the pipes is in direct ratio to the heat absorbed by the boiler 
from the fire. Thus, if one house only be at work, there is only 
the water of one arrangement to be heated; and, consequently, 
only one return of cold water into the boiler, the rest being shut 
off. Now, if the water be shut off into the box, that is, the 
mouths of the flow-pipes stopped, there is no circulation ; hence, 
there is no return of the cold water into the boiler, and, conse- 
quently, no absorption of caloric or combustion of fuel. Of 
course, more fuel is required to heat the four houses, than would 
be required to heat one, for the reasons stated, that the larger 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 207 

the body of cold water flowing into the boiler, and the larger 
the body of warm flowing from, it, the more heat is carried 
away ; hence, the more specific caloric is required, and the more 
combustion of fuel to produce it. But the proportion of fuel 
consumed to the proportion of heat generated by the pipes is 
found to decrease as the radiating surface is increased. This 
decrease amounts to nearly one third ; for it is found that eight 
separate houses, or departments of a house, can be heated by the 
same quantity of fuel which it formerly required to heat five. 
This calculation was supplied to me by an intelligent gardener, 
of extensive experience, who made it from strict investigation 
into the working of the system under his own charge ; and the 
statement is corroborated by the fact, that no case has occurred, 
to my knowledge, among many with which I am acquainted, and 
have examined, that has failed to give satisfaction. 

This system has not the complex character which some have 
assigned to it, and which, at first sight, it would appear to pos- 
sess; and, as to its cheapness, I believe little can be said about 
it, when placed in comparison with other hot-water apparatuses. 
I have had no means of calculating the difference, if any, 
between this apparatus and as many single ones as it may be 
substituted for. But it certainly appears, that four houses 
heated with one boiler and one furnace, would be cheaper than 
four houses heated with four distinct boilers and furnaces, the 
quantity of piping in both cases being equal; for then, three 
boilers and furnaces, or the cost of them, would be saved. This 
difference, however, will depend very much upon the distance 
the pipes must travel before entering the different houses. 
When the houses are situated close to each other, the difference 
must be very considerable. Some apparatuses of this kind have 
no box attached to them, and work directly to and from the boiler. 
I consider the box, however, as a very important appendage ; 
not only because it affords greater facility for working the 
apparatus, but because any of the other arrangements may be 
repaired more easily, and parts may even be taken away with- 
out in the least affecting the working of the rest 

As I have already stated, pipes, in reality, radiate a very dry 
heat ; though many think otherwise, because the air of a hot- 



208 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

house, so heated, is generally less arid than one heated by a hot- 
air stove. This arises from the fact, that, by hot-water pipes, a 
much larger radiating surface is presented to the atmosphere of 
the house than by any other method, and the heat is radiated at 
a lower temperature, and more equally diffused; hence, less 
moisture is carried upwards by currents of heated air and 
deposited on the glass by condensation. Thus, it is clear, that 
the larger the heating surface that is acted upon by the air, and 
the lower the temperature of that surface, the less moisture will 
be drawn from the plants and the atmosphere of the house. It 
is always desirable, however, to provide against aridity in the 
atmosphere, as heated air will have its supply of moisture, come 
from where it will ; and if it cannot draw it from anywhere else, 
it will draw it from the plants, or whatever can supply the larg- 
est quantity under its influence. For this purpose, a number 
of troughs are made to fit on the pipes, made of zinc or gal- 
vanized tin. These troughs may likewise be made of earthen 
ware, and perhaps more cheaply than of zinc, though more lia- 
ble to be broken. They may be filled with a syphon from the 
pipes, or by a common water-pot. When moisture is required 
in the house, an agreeable evaporation will be given off, and 
which can be rendered still more healthful, by putting in a few 
bits of carbonate of ammonia among the water, or common 
pigeon's dung, or guano. As the water warms, ammonia will 
be evolved into the atmosphere and greedily absorbed by the 
plants. 

In recommending this system to the notice of those who may 
be entering upon the erection of hot-houses, we would state that 
we recommend it not only upon our own experience, but also 
upon that of others, whom we consider much better qualified 
to decide upon its merits. Nor do we mean to assert that it is 
the ne plus ultra of a heating apparatus, although, under certain 
circumstances, it is the nearest approach to it that has yet come 
under our observation. In making this statement, we do not 
wish to dispute the judgment of those who think differently, and 
who have opposed it more from a feeling of groundless distrust, 
than from any fact they can bring to bear against it. We have 
conversed with many who would prefer heating each house with 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 209 

its own fire and boiler, and be at the additional trouble of attend- 
ing them too. This, however, springs from a fear entirely with- 
out foundation, and we are convinced that a little experience in 
the working of this double system of heating would so prove it. 
It is a very singular attachment which some people have for old 
methods and customs, that they will unflinchingly adhere to 
them, however little merit they may have to recommend them. 
Some individuals, with a self-sufficiency altogether incompatible 
with knowledge, will smile or sneer at what they are pleased to 
call the folly of enthusiasm, and, without seeming to be in any 
way sensible of the importance of whatever tends to the im- 
provement of horticulture, regard these innovations merely as 
idle speculations of men who have nothing else to do but invent 
them ; and while we cannot guard too much against the adoption 
of methods that will prove inconvenient in practice, although 
supported by theory, it is an injury to gardening, as an art, to 
give an unqualified opposition to systems that have proved their 
superiority, and are still capable of great improvement. This 
plan is not introduced under the deceptive cognomen of cheap- 
ness. Its cost will very much depend upon the circumstance of 
position, and may, after all, be much less than some of the costly 
and cumbrous apparatuses that are now in use. The easiness 
with which it is worked adds an additional item to its worth, 
for, when once set agoing, and understood, the veriest novice 
could manage it. ^ 

* It is the common fate of new systems connected with the art of 
horticulture, that they are eulogized beyond their real merits by their 
advocates, and decried as strongly by their opponents ; for every new 
system has always both friends and foes, each of whom are unwilling to 
adhere to the naked truth, and equally incapable of appreciating its 
merits with exactness. "When a person invents, or fancies he has 
invented, something new, he is too much inclined to set a high value 
upon it ; for, if it has cost him much labor, he is unwilling to think he 
has been diligent in vain. He, therefore, magnifies what is merely an 
alteration into an improvement, and probably prevails upon the imagi- 
nation of others to fall into a false approbation of the system, and to 
regard that as a valuable desideratum which, at the best, was only a 
novelty. If durability and economy in working be allowed to constitute 
any part of excellence in a system, then this one has especial claims to 
our notice ; a fact which cannot be said of many others. 



210 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 




VARIOUS METHODS OF HEATING DESCRIBED IX DETAIL. 211 

Fig. 43 shows a house wherein provision is made for increas- 
ing the heating surface, when more than a very moderate degree 
of heat is required from the pipes. A box or tank, made of wood 
or zinc, is placed under the stage, and passes all round it on a 
level with the pipes. This tank is supplied by a branch pipe a, 
proceeding from the flow-pipe, and is provided with a tap at b, for 
shutting off and on the water when necessary. This is a most 
convenient arrangement ; for, if a moderate heat only be required 
from the apparatus, then the pipes will be sufficient, and a very 
small fire will be required to heat them, as the quantity of water 
is small. When it is found necessary to increase the tempera- 
ture of the house, the pipes beino; then tolerably warm, the 
water from the flow-pipe is admitted into the tank by opening 
the tap. The heat of the pipes is slightly reduced, but the 
radiating surface is increased, and the temperature of the house 
rises by an equal distribution of heat. It might be supposed 
that a quantity of specific heat is lost to the atmosphere, by 
drawing it from the pipes and throwing it into a body of cold 
water. Not so, however, as a little consideration will make 
sufficiently clear. Thus, if the atmosphere of the house be at 
45 degrees, the water in the tank will be at 45 degrees also. 
Now, suppose the tank and the pipes to contain equal bodies of 
water, then, if the pipes communicate a portion of their heat to 
the tank, the temperature of the water in the tank will rise just 
as much as the water in the pipes will fall ; for, if two equal 
bodies of water, at different temperatures, are mingled together, 
the temperature produced by the mixture will be the mean of 
their previous temperature. Suppose, for instance, that the 
temperature of the water in the pipes was 300, and that in the 
tank 45 degrees, and that, by the opening of the tap, the hot 
water in the pipes, and the cold water in the tank, were inti- 
mately mingled together, then the temperature of both would 
be 122-5 degrees. The temperature of both has been equal- 
ized, but the atmosphere of the house has lost none by the 
change, but rather gained, as the tank being 77 degrees 
above the temperature of the atmosphere, more heat will be 
diffused than with the pipes alone at double the temperature, 
and the object will be gained, namely, that of preventing the 



212 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

plants from being subjected to a high temperature, that are situ- 
ated in the vicinity of the pipes. In the drawing, (Fig. 43,) 
the flow and return pipes are placed together, the other side 
being heated by the flue from the fire. This arrangement is 
intended to economize heat, and to save the expense of pipes, 
which, in some places, might be an object of importance, and 
even if they were not so, the plan is decidedly good. As for the 
tank, it is an admirable contrivance. Not only is the evil of 
having highly heated pipes for weeks and months together, 
directly under the roots of plants, prevented, but when the tank 
is once heated, a more agreeable and healthy warmth will be 
produced, and the equilibrium of temperature be maintained 
for a much longer time. 

The tanks used may either be wooden or metallic. The lat- 
ter are preferable, both on account of durability and radiation 
of heat, although wooden ones are much cheaper, and answer 
the purpose perfectly. Wooden tanks, if the wood be kyanized, 
or otherwise treated with a metallic solution, will last for many 
years, and produce a very agreeable warmth. Galvanized iron 
and zinc are now in common use for this purpose. The dura- 
bility imparted to it by the process of galvanization, which pre- 
vents oxidation, is evident from the number of articles made 
of this material and exposed to the atmosphere. For horticul- 
tural purposes, this article is likely to become exceedingly 
useful; as every one is aware of the injury which ordinary hot- 
water pipes, and other metallic substances used in horticultural 
erections, are liable to from rust. Tanks made of this material 
give out their heat much more rapidly. But it must be consid- 
ered that the same circumstances that would render them more 
quickly effectual, would also render their effect more transient. 
For pits and very small houses, the pipes and tanks might be 
made of this material. Its cheapness and lightness are impor- 
tant advantages in its favor; for, when heavy-cast metal pipes 
are conveyed to a great distance, the cost of carriage will nearly 
amount to the same sum as would purchase galvanized iron or 
zinc tanks, and convey them too. 

In using this kind of tanks, the utmost care ought to be 
taken in supplying them with water. They ought never to be 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 213 

over one third or half full ; the less water that is in them the 
better, compatible with safety. To work well, the water ought 
never to boil into them, otherwise the force of 'the steam will 
expand the metal, and, if the heat continue, it is liable to burst. 
Fig. 44 represents a house heated with a tank made of galvan- 
ized zinc. Next to the boiler there is a short piece of cast-iron 
pipe which prevents the zinc from being affected by the imme- 
diate action of the fire. The house from which this sketch was 
taken has been in use for some years, and has given perfect sat- 
isfaction, while the original cost was very small. The principal 
objection to the use of this material for heating purposes, is, as 
I have already stated, the rapidity with which it is heated, and 
the rapidity with which it parts again with its heat. This cir- 
cumstance renders it a good conductor, but a bad retainer, of 
heat ; useful where speedy and immediate action is required, but 
useless where a slow and long-continued radiation is necessary 
at a very low temperature, as, for instance, for bottom-heat, 
for propagating-beds, and for plant-stoves. In such circum- 
stances, we should decidedly prefer wood, particularly for the 
first-mentioned purposes. In green-houses, and even in forcing- 
houses, it may answer well ; for it must be admitted that the 
source of heat must ever be looked for at the boiler, not in the 
material of which the tanks or pipes are made. And, although 
the advantage of employing a material that will absorb the heat 
given off from the source to any extent, and part with it gradu- 
ally, must be apparent, at least, when it is an object to take 
advantage of the heat so absorbed, store it up, so to speak, with 
the view of employing it when the action of the apparatus 
becomes enfeebled. The law by which this is effected is the 
same as that by which the two bodies of water become equal- 
ized in temperature by admixture as described on page 210. 
This is the law of equalization, which constantly tends to bring 
all bodies to an equal temperature. If, for instance, the hot w T ater 
from a boiler be admitted into two separate tanks, one of wood 
and the other of zinc, then, by placing the palm of the hand upon 
the wooden tank, it will feel agreeably warm, while the zinc 01 
tin one would be quite unbearable, if not burn, and this while 
the temperature of the water in both tanks was the same. The 



214 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



Fig. 44. 




VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 215 

reason is, the metal is a good conductor, and quickly conveys 
away the heat from the water by imparting it to a colder body, 
while the wood is a bad conductor, and retains it. Again, the 
metallic tank will have the same temperature as the water 
within, before the wooden one is sensibly warm. In fact, the 
wooden tank retains and accumulates the heat, while the metal- 
lic one gives it off as soon as it receives it. None of this heat, 
however, is lost to the atmosphere of the house; for though the 
wooden tank parts with its accumulated heat more slowly, it as 
certainly parts with it, in the course of time, as the metallic one. 
It parts with its heat gradually till it is reduced to the same 
temperature as the atmosphere around it. A house heated with 
a wooden tank will maintain an average temperature with less 
expenditure of fuel than a thin metallic one, the other circum- 
stances being equal, which is accounted for by the fact that 
when a house is suddenly heated, the warm air is forced rapidly 
upward, and, coming in contact with the glass, is rapidly cooled, 
descends, and is again warmed, till the warming surface is 
entirely deprived of its heat; then the temperature falls. On 
the other hand, when the heat is disseminated at a low temper- 
ature, the atmosphere is less agitated, and the ascending air 
less rapid in its motion. Not so much escapes through the laps 
of the glass, or is cooled down by the external cold upon its 
surface ; and hence, the same quantity of specific heat maintains 
a given temperature for a longer time, when gradually given off, 
than when suddenly given off at a high temperature. 

Although the sudden rise and fall of temperature by thin 
metallic tanks be apparent, we do not condemn their use for all 
purposes. As we have already said, they may be profitably 
used in many kinds of erections, and for various purposes ; and 
I consider them worthy of more extended trials. But I do not 
believe that they will ever supersede cast metal pipes for the 
general purposes of heating by hot water; and for a retention- 
tank, I would decidedly prefer wood. Fig. 45 represents a 
house with a wooden tank, in which the water circulates by 
various divisions, after it enters from the flow-pipe. This tank 
was erected in a plant-house beneath the stage, as shown in the 
end section, Fig. 46, which may be objectionable as regards 
19 ~ 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 217 

its position, but the chief object was to hold and retain a sup- 
ply of warm water, which it did admirably, and effectually 
warmed the house besides. The manner in which this tank 
retained the heat after the fire had ceased to burn, impressed 
me with the idea that heat could be drawn off from the regular 
apparatus, and applied afterwards when necessary, or for any 
other purpose. I believe the heat generated by wooden tanks to 
be most favorable to the structural development of plants, as con- 
taining more moisture than heat radiated from either iron or 
brick, because the temperature is lower. 

We have already remarked that the tank system of heating 
hot-houses has but very lately been brought into general notice, 
and still receives much less attention than its utility, simplicity, 
and economy claim for it ; and where it has been used, it is 
chiefly as a medium of bottom-heat, for which it is undoubtedly 
superior to anything that has yet been applied. The efficiency 
of tanks in supplying atmospheric heat has been doubted by 
some and denied by others, without, however, as far as I can 
learn, bringing any practical facts to bear upon the subject. I 
am convinced that the system, rightly applied, will prove the 
doubts to be entirely without foundation. Simplicity in any 
system of heating is a point of incalculable importance ; and 
when economy and adaptibility are combined with it, a claim is 
presented which facts only can overthrow. It is very true that 
we practicals are, many of us at least, prone to adhere bigotedly 
to any method with which we are acquainted, and which we 
have already proved safe and simple, and are unwilling to 
believe that any other method can be safer and simpler than 
itself. Gardeners are proverbially a cautious and thoughtful 
class of men ; perhaps seldom directly opposing principles 
founded upon theoretical deductions, but frequently slow in 
instituting experiments with the view of establishing their truth. 
In these days of invention and progress, it is the duty of every 
one engaged in horticultural pursuits, and particularly garden- 
ers, not only to make themselves acquainted with the views and 
opinions of other persons, but to test, by various counter-experi- 
ments, the conclusions they have drawn. No man is justified 



218 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

in regarding his knowledge of any system well-founded, except 
upon experiments and observations of his own. 

Gardeners are, of all others, the best qualified to decide upon 
the merits of any system of heating hot-houses, and to ascertain 
its effects upon vegetable life. They are, by necessity, familiar 
with the habits of plants ; and, by an instinctive practical knowl- 
edge, (if nothing mGre,) they are less likely to be deceived by 
the peculiarities produced by heat and cold, dryness and moist- 
ure, either in deficiency or in excess. The gardener is able to tell 
whether his plants be in vigorous health, or the reverse ; whether 
they are suffering from atmospheric impurity, aridity, or stagna- 
tion; and, besides, the necessities of culture compel him to 
study the causes of such changes and conditions. All gardeners 
are aware that causes the most dissimilar will produce results in 
every way identical, while the self-same causes, repeated with 
the greatest care, and under circumstances where it was appar- 
ently impossible for them to be at variance with the first, will 
nevertheless produce results totally different ; and the universal 
axiom, that like causes produce like results, would sometimes 
appear to be set at naught. 

It has ever been a desideratum, as regards the heating appa- 
ratus, especially the hot-water kind, that there should be among 
gardeners a perfect knowledge of their details, and of the man- 
ner of repairing them. It is true we know when they become 
warm, and when they cool ; but, as for the rest, once erected and 
the workmen gone, they are like a watch, or a doctor's prescrip- 
tion, — they may go wrong, and become unworkable, but we 
cannot put them right, nor scarcely discover what is the matter 
with them, till we send for the tradesman ; and then, after an 
hour or two pulling and hammering, dusting and besmearing our 
plants, turning everything in the house topsy-turvy, lo ! we are 
told that a joint had cracked, a collar had split, or some such 
mishap had befallen our apparatus. Facts of this kind will be 
in the experience of every one who has had much to do with 
heating apparatus. Now what I would urge is, that no part of 
a heating apparatus should be under ground, or buried in brick- 
work so far as it is concerned with the interior of the house, 
Not an inch of it ought to be covered up with anything. It 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 219 

ought to be all exposed, as far as possible, and of easy access. 
Moreover, let it be simple in its arrangements ; the simplicity 
of any system is a plea in its favor. Some people, however, 
despise simplicity, and would baptize everything about them with 
confusion and complexity. We have met with people who fancy 
that their green-house could not be heated without an array of 
pipes, winding here and there, as intricately arranged as the 
wheels of a watch, and as useless for the heating of their house 
as the pillars that support the portico of their dwelling. One 
would think that they admired cast metal pipes more than their 
flowering plants. 

One of the chief commendations of hot water, as a heating 
power, is the facility with which you can bring it in contact 
with the atmosphere of the house ; however simple the manner 
in which it may be applied, it is not the less effectual ; and how- 
ever commendable in other respects the warming of hot-houses 
by improved methods of hot air may be, the channels and 
chambers, the numerous hot and cold air drains, the under- 
ground building of brick-work, and the multifarious intricacies 
of its arrangements, are sufficient to deter any person from the 
erection of such a complicated affair. This will be apparent 
from a glance of the drawing of Meek's improved method of a 
hot-air heatiug-apparatus, given on page 197. Such a concern 
may do very well on paper, but it will not do in practice. It 
may answer admirably as a plaything for amateurs, who have a 
fancy for it, and nothing else to do with their time but to amuse 
themselves with the motions of air ; but, as a method of warm- 
ing a hot-house, no sane person will adopt it, when he can have 
the thing done by a simple tank and boiler at half the expense. 
As a system, it is good for naught. No person who understands 
it will adopt it ; and those who do not know it, but will have it, 
let them try. 

The tank system may justly be regarded a real improvement 
in heating, whether for top or bottom ; and it is the simplest, 
and perhaps the cheapest, that has yet been brought under pub- 
lic notice. The sketches we have given are probably not the best 
that could be adopted. It is yet open to great improvement, and 
it would be premature, at present, to hazard an opinion upon 
19* 



220 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

what may hereafter be effected by it, by the friction of one idea 
against another in the course of experience. For small pits, 
filled with young stock, it is invaluable, as a pipe may be car- 
ried from a boiler, heating other structures, into a pit near by ; 
and, these being easily covered at night, a sufficiency of heat 
may thus be conducted into them to keep the plants safe 
during the winter, without much increase of fuel, or any with- 
drawal of heat from the structure for which the apparatus was 
originally constructed. Green-houses are generally too much 
crowded in winter, and the adoption of dry pits for the conserva- 
tion of plants that are somewhat hardy in their nature, is not 
so common as it ought to be. Pits might be so arranged 
as to obtain the superfluous heating power from other houses. 
This, in some instances, has been done, and it is likely that 
more will ere long be done in the same way ; for if the vast 
amount of fuel, consumed by the general methods of heating, 
could be economically applied, without waste, it is not exaggera- 
tion to say that at least one third could be saved. 

The hygrometrical and ammoniacal condition of the atmos- 
phere of hot-houses has not received that attention, in connec- 
tion with heating, which the importance of the matter evidently 
demands. We have books enough teaching us the effects of 
certain volatile and subtile fluids upon vegetable life, and exhib- 
iting a multitude of facts which no person w r ill venture to dis- 
pute ; yet, in this matter, we practicals have, in a great measure, 
been deaf to the teachings of science, and blind to the lessons 
of nature. Practically, or experimentally, we have made but 
little inquiry whether invigorating or contaminating gases 
abounded in our hot-houses. Now, nature is either a good or 
a bad teacher, just in proportion as our knowledge of her im- 
mutable laws is limited or comprehensive. When we confine 
plants in a case of glass, as in a green-house, if we give them 
soil to grow in and water to drink, we are apt to think they 
ought to be contented ; and if they do not thrive well and prove 
productive, we call them ungrateful, or very difficult to rear. 
Now, we ought to consider that plants feed by their leaves as 
well as by their roots, and that the volume of air in which the 
leaves are expanded, requires to be as regularly moistened and 



VARIOUS METHODS OF HEATING DESCRIDED IN DETAIL. 221 

manured, as the body of earth in which they grow. It may 
appear vague and visionary to talk of manuring the atmosphere 
of a hot-house, but the thing is in reality neither so vague nor 
yet so visionary as it seems ; for here science comes to our 
aid, and not only defines the vagueness, but converts the vision 
into a practical reality. It proves to us, both the benefits of 
manuring the air, and the manner of doing it. We know that 
plants derive a large portion of their food from the atmosphere ; 
and we know, also, that the arid atmosphere of a hot-house is not 
always charged to a proper degree with these life-giving gases. 
An impoverished atmosphere must have the same effect as an 
impoverished soil. This is a well-known fact, and requires no 
demonstration to prove it. We are well aware that many 
plants will grow luxuriantly for years, suspended in the air, pro- 
viding they be kept in a condition calculated to sustain them ; 
but deprive them of these gases, and they will die, — deprive 
the atmosphere of its humidity, and they will quickly cease to 
exist as living plants. These vegetables absorb carbonic acid, 
ammonia, and water, from the atmosphere, by their leaves, even 
more abundantly than by their roots. This is especially the 
case with plants cultivated in pots ; their roots being circum- 
scribed into a small space, the nourishment is speedily exhausted, 
and if the atmosphere be at the same time robbed of its gaseous 
elements by artificial heat, the plants must perish, if this defi- 
ciency is not supplied to them by artificial means. 

We have seen, that plants, even of a ligneous nature, will 
grow, form lignin, and proteine compounds, while suspended in 
a moist warm atmosphere, much in the same manner as plants 
do when growing in the soil. The amount of mineral matter 
they contain is indeed very small, and may be derived from the 
dust continually floating in the atmosphere, which is dissolved 
as it falls upon the leaves, and is absorbed with the atmospheric 
fluids. Here, then, we have plants subsisting upon the ingre- 
dients of the atmosphere ; and experiments seem to prove that 
all plants are nourished by the same substances, in variable 
proportions, the chief of which are carbonic acid, water, and 
ammonia. 

Experience has already proved the beneficial effects of these 
substances as fertilizers, not only of the soil, but also of the 



222 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

atmosphere. Plants watered with a weak solution of the salts 
of ammonia (smelling salts) will, in a few days, show their 
invigorating effects ; and plants grown in a hot-house, with 
the atmosphere impregnated with ammonia, will exhibit, in 
a manner equally as striking, its beneficial influence. Every 
gardener is aware that plants, growing in frames or pits 
heated with fermenting manure, will, under ordinary circum- 
stances, evince a much greater degree of luxuriance than in 
any other situation. In fact, dung-beds are considered an an- 
tidote for nearly every disease that plants are heir to, and not 
without a well-grounded knowledge of their effects ; and 
hence, when a gardener wishes to invigorate sickly plants, he 
straightway plunges them into a hot-bed, and if there be any 
vitality left in the plant, it seldom fails in pushing out vigorous- 
ly. Now nothing is more obvious than the fact that neither the 
heat, nor the moisture alone, produced this result ; for if the 
plant had been plunged in a hot-bed warmed with the combus- 
tion of fuel, in nine cases out of ten the result would have been 
the very reverse. In fact, it is found, by long experience, that 
neither heat nor moisture alone will compensate for the removal 
of a sickly plant from the congenial warmth of a well-prepared 
dung-bed. Now, the question which presents itself for solution, 
in regard to this mode of heating, is, What is the cause of this 
difference, and how can it be otherwise produced ? If we con- 
sider the effects due to the gases already mentioned, to be fully 
established, we will find that the secret of all this lies in the 
stimulating gases of the manure, which constantly surround the 
plants when exposed to the mild heat of a dung-bed. The old, 
and now almost obsolete, plan of warming forcing-houses with 
accumulated masses of fermenting manure, is well known ; and 
the luxuriance of vines, forced by this method, is as well known 
as the method itself. This luxuriance was produced by the 
ammoniacal and other gases evolved during the process of fer- 
mentation ; and though this method of forcing has been entirely 
laid aside, on account of its unsightly appearance, and the incon- 
venience of keeping up a constant supply of well-prepared ma- 
nure, still the merits it possessed, by its ammoniacal properties, 
have not yet been secured in any other mode of heating. 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 223 

Suppose, then, that we have already solved the first part of 
the problem, by attributing these results to the beneficial action 
of gases arising from fermenting manure ; let us consider how 
we can produce those gases, under other circumstances, i. e., with- 
out the presence of manure. 

Ammonia is the result of a combination of the two gases, 
hydrogen and nitrogen, and has been hitherto known to gar- 
deners, and applied by them, chiefly in the state in which it 
exists, and is produced by the decomposition of animal and veg- 
etable matter, as in the formation of dung-beds, from which we 
can perceive it escaping in an uncombined state into the atmos- 
phere. It is easily distinguished from all other gases by its 
powerful, penetrating odor. It remains, however, but a short 
time in this state, as it is speedily absorbed by porous sub- 
stances, and by living plants, and combines with other gases, 
forming compounds ; with carbonic acid, for instance, forming 
the carbonate of ammonia of the shops, from which it can read- 
ily be disengaged and evolved into the atmosphere of a hot-house. 
Ammonia, in the state of a carbonate, is exceedingly volatile, and 
when a small portion is mixed with water, and the temperature 
raised to about 112 degrees, a large quantity of ammonia is 
evolved. This will be still better effected by mixing a small 
quantity of potash, soda, or lime, with the water in which the 
ammonia has been absorbed. The salt which held the ammo- 
nia in combination is taken up by these alkalies, and the ammo- 
nia, being exceedingly volatile, escapes into the atmosphere. 

By dissolving the sulphate or carbonate of ammonia in hot- 
water tanks, or in thin troughs placed over the pipes and flues, 
an atmosphere may be produced strikingly similar to that of a 
dung-bed, and capable of producing nearly similar effects. 
Dung-beds are probably the most natural methods of applying 
artificial heat to plants ; and it is yet doubtful if we shall ever 
be able to supersede them in their invigorating influence, 
although much may be done to modify the existing evils of arid 
and unwholesome atmosphere in hot-houses. The mixture of 
guano, pigeon's dung, and various other substances, gives off 
large quantities of ammonia in warm water, and may be used 
with advantage instead of its salts. Tanks afford an excellent 



224 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

means of effecting this purpose, and are, not only on the score 
of simplicity and economy, but, also, in an ammoniacal and 
hygrometrical point of view, the best methods of producing heat 
with which I am acquainted. 

The principal kind of structures to which the tank system of 
heating has yet been applied, to any extent, in England, are 
what are termed forcing-pits ; and in these it has been exten- 
sively used, with much success. In this department of forcing, 
it has proved one of the greatest improvements of modern times. 
In England it is used on a large scale, in the culture of pines, 
vines, melons, cucumbers, &c, during winter ; and, although 
in this point of view, it may not be deemed of equal importance 
in this country, where early forced fruits and vegetables are less 
demanded, it is, nevertheless, calculated to be of immense value 
to horticulturists in general, and plant-growers in particular. 
There is little doubt, but, ere long, an increasing demand for 
early forced fruits and vegetables, fresh from the forcing-house, 
will stimulate enterprising individuals to the erection of those 
cheap and simple structures, which could scarcely fail of being 
a profitable investment. A given space, covered with a glass 
roof, and otherwise protected, requires a comparatively small 
amount of fuel to maintain a tolerable degree of warmth in the 
soil, much less than is generally supposed. It is not my pur- 
pose to enter, at present, into the details of this question, and I 
merely notice it in connection with the subject of heating. By 
many it may be regarded as a mere speculative theory, which 
it certainly is, yet I think it worthy of more serious considera- 
tion. 

In many of the English nurseries, tanks are used for stimu- 
lating the growth of their young stock, and in many kinds the 
annual growths are indeed remarkable. We have seen camellias, 
one year from the graft, as strong and vigorous as plants three 
or four years old under the old method of culture. Almost all 
kinds of green-house plants are benefited by being kept in tank 
pits, and we are inclined to think, if tank pits were more gener- 
ally used by the nursery-men of this country, they would have 
their plants easier got ready for market, and they would require 
much less time to do so than is generally the case. 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 225 

For amateurs wishing to " try to grow many things," but 
who have little time or money to spare for such purposes, one 
of these pits is just the thing he requires. A small pit, of this 
nature, with a very little attention, would keep a considerable 
number of green-house plants over the winter, and enable him 
to preserve a plentiful stock of bedding-out plants, such as ver- 
benas, petunias, calceolarias, heliotropiums, penstemons, and 
many other pretty little things for the decoration of the flower- 
garden in summer. How much more pleasant and profitable 
would it be, for lovers of flowers, to have a little pit erected in 
some snug corner of their garden, instead of losing all their 
roses in winter, and storing their drawing-room plants, — their 
oranges, their camellias, their gardenias, oleanders, &c, — into 
the cellar, from which, of necessity, they are frequently taken 
half dead. Such a pit as I allude to may, or may not, be made 
to comprehend a narrow pathway along the back, — this would 
certainly be the most convenient, — and this portion might be 
covered with boards or shingles. This path would greatly facil- 
itate the operations of watering, &c. Whether such a pit ought 
to be sunk below the ground, or placed on a level with its 
surface, will depend altogether upon the nature of the situation. 
Thus, if the position be a dry one, or admits of being made so 
by drainage, it should, by all means, be sunk two or three feet 
below the surface. But if the situation be very damp, it would 
certainly be bad policy to sink it so much ; for whatever advan- 
tage it would gain in the way of protection, would be more than 
counterbalanced by the dampness which would be unavoidable. 
A pit, sunk in a dry situation, requires less fuel, even in the 
severest winters, than people generally suppose ; and if covered 
from the frost, and kept dry, many plants will live over winter 
without fire at all. Plants are very much like animals, in re- 
gard to warmth ; wheji once accustomed to a high temperature, 
they must have it continually ; but inure them to the cold of 
autumn, and they will do with less heat in winter. This is 
not saying that we can change the nature of plants, and make 
them to endure a lower temperature than they can possibly, 
under any circumstances, bear. But we know that plants may 
be brought into a condition to enable them to survive a much 



226 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

greater amount of cold than they could otherwise have endured, 
and this, too, apart from the application of artificial heat. When 
half-hardy plants are destroyed by frost, its effects are most 
frequently visible at the collar, or lower part of the stem, arising 
from the intense action of the cold at the surface of the ground, 
which, in combination with moisture, first contracts and then 
expands the principal sap-vessels of the plants. 

The annexed cut represents a double range of plant-pits, 
heated by wooden tanks. These tanks are supplied from a 
small boiler, placed in the centre, between the two pits ; a, end 
section, shows the end of the tank, which is about six inches 
deep, and divided into two compartments, by placing a slip of 
wood up the centre, leaving a space at each end, for the water 
to circulate round. The arrows show the course of the water 
in its progress round the tank ; the flow and return pipes are 
represented by dotted lines. These tanks are merely shallow 
boxes of wood, occupying nearly the whole inner area of the 
pits, and resting on piers of brick, or posts of wood ; rough 
pieces of wood are laid crossways over the tanks, and a layer 
of broken bricks, (or sawdust, if the pots are to be plunged, 
which is desirable,) which forms the bottom, or floor, of the pit. 

It is truly surprising how very little fire is required to main- 
tain a perceptible warmth in these pits ; and the growth of plants 
or vegetables of any description is astonishing. In some nurs- 
eries these pits are kept continually at work. The lights are 
entirely thrown off them, and the tops thoroughly exposed to 
the air ; this prevents them from being drawn up tender and 
etiolated, and while their roots are stimulated with an agreeable 
warmth, they have, nevertheless, all the strength and hardiness 
of plants grown in the open air. 

For the growth of early melons and cucumbers these pits are 
admirably adapted ; they are equally efficient, without having 
the disadvantages of dung-beds. Their neat and tidy appearance 
gives them a place beside the other hot-houses, (which is not 
the case with hot-beds of manure,) to none of which they 
yield, in point of utility or interest. 

If there is any one branch of exotic horticulture that possesses 
more extended interest than another, it is, undoubtedly, the cul- 



VARIOrS METHODS OF HEATTN'G- DESCRIBED EN~ 



DETAIL. 22"7 



Fig. 47. 




20 



228 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

ture and early forcing of the grape-vine. The increasing im- 
portance of this branch of gardening will justify me in devoting 
a few pages to that subject. The culture of this fruit occupies 
a very high position in this country ; volumes and pamphlets 
innumerable have been written about it, by practicals, theorists, 
and experimentalists, each one supposing he has discovered 
something, which, for want of more extended information, he 
calls " new," in the managing, heating, or ventilating of his 
vineries, when, lo ! another starts up and knocks it on the head, 
and proposes a new nostrum ; and every one is sure to find 
some ignorant enough to follow his advice. It might not be out 
of place here, to discuss some of the most important points which 
an extended experience has proved to be desirable, in the heat- 
ing of structures for the culture of the vine. 

And, first, let me remark, that nothing is more creditable than 
the use of the readiest and cheapest means at hand for securing 
a definite result. Whatever system may be thought of, it is 
desirable to understand the principles upon which it rests for 
its success. It must be borne in mind, in the outset, that no 
care in the culture of the vine, under glass, will compensate for 
a contaminated atmosphere, which should, at all times, approach 
to the natural summer purity and warmth. 

Were we to analyze and bring into view the first principles 
of horticulture, and make ourselves masters of the various effects 
produced upon the grape-vine under glass, and the causes, we 
should often smile at the ludicrous importance we attach to par- 
ticular methods of practice. A blind man, by habit, will often 
walk along a devious path, with quagmires and pitfalls on either 
side of him, and safely too, whether at midnight or noon-day ; 
and we often follow the example of the blind. We, in one way 
or another, acquire the faculty of performing certain operations 
with a life-like certainty, though in the same degree of mental 
darkness as regards the power of deviating from the beaten 
track without committing egregious errors. In all such cases, 
there can be no doubt that it is wise to follow the old trodden 
path, till we can more plainly see which is the safest for our 
particular case. It does not so much signify which of the best 
methods we adopt, provided the science of culture has given us 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 229 

sufficient light upon the nature of the endless variety of means 
and methods that are before us, which, however defective they 
may seem in the hands of the inexperienced, may be safe and 
certain in the hands of the skilful practitioner. 

It cannot be admitted, however, that in carrying out this 
principle it is unnecessary to scrutinize, with the utmost exact- 
ness, the facts for or against any particular system, which the 
fancy of gardeners or amateurs may choose to follow. The very 
fact that there are so many systems of warming hot-houses, 
gives increased force to the call for minute record of experi- 
ments. Upon no safer principle can our knowledge of horticul- 
ture be based, so that those who are its patrons and votaries 
may follow principles, founded upon facts, and not upon specula- 
tions. Hence they would not have to endure the inconvenience 
and risk of being dependants upon plausible theories, which 
practice may prove to be absurd. 

A great deal that might be said on vineries, in regard to heat- 
ing them, can have but a local application ; and, in some places, 
no application at all, inasmuch as the diversity of climate in the 
different states would render the erection of an apparatus at one 
place necessary, which would be absolute folly in another. The 
erection of a powerful and expensive heating-apparatus is only 
required where the forcing of the vine is desired in winter, under 
difficulties of intense cold and long-continued frost, as in New 
England. To these latter circumstances the following method 
will chiefly apply. 

Figure 48 shows the plan of a winter vinery, i. e., one for 
forcing in winter; a is the border, underneath which is an 
arch of brick, forming a chamber, through which the hot- 
water pipes are made to travel, after going round the house 
inside for atmospheric heat. The cold water returns again into 
the boiler at b. 

As far as I can learn — and I have made many inquiries — 
this system of applying heat, in connection with vine-growing, 
has not yet been adopted in this country ; still, it may be in 
use, since the obvious utility of it must have been apparent to 
those who are engaged in the culture of hot-house grapes. To 
recommend such an expensive system as this, for all occasions 



230 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



Fig. 48. 




pn 



^7 



I 

1 

I 



i 

I 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 231 

and under every circumstance, would be folly. But its utility 
in winter-forcing, especially where the soil is damp and natu- 
rally cold, will be obvious to any one of much experience in 
these matters. The greatest success has attended the applica- 
tion of border-heating, in England, where an enormous amount 
of money and labor is annually expended upon the forcing of 
grapes, and where they are produced in great perfection all the 
year round. 

I have said that where early forcing is practised, and the soil 
and sub-soil of a cold, retentive nature, the adoption of some 
method similar to the above is almost indispensable to general 
success. I wish, however, to be rightly understood, and not to 
mislead, and therefore advert to what every gardener knows well, 
that good grapes are sometimes produced under the entire neg- 
lect of all the ordinary precautionary measures resorted to by 
good gardeners for the purpose of securing success. 

In support of this method of heating borders, I will briefly 
advert to the opinions of some of the leading gardeners in Eng- 
land. Mr. Fleming, gardener to the Duke of Sutherland, at 
Trentham Hall, writes to the Gardener's Chronicle, four years 
ago, to the following effect : — " Shrivelling was common here, 
until the system of keeping up a bottom heat in the vine bor- 
ders was introduced. Since then there has been no appearance 
of it, except in a late house last year. In the month of August 
we had a great deal of rain, which penetrated .the border, and 
the weather was for a few days very cold, and the grapes, which 
up to that time were swelling beautifully, received a check, and 
shortly after many of the fruit-stalks shrivelled." 

In the same paper Mr. F. makes the following statement, 
which is the strongest evidence of the utility of the system that 
has come under our notice : — "I am so convinced," says he, 
"of the advantage of this practice, that I would prefer the 
introduction of flues under every vine .border about the place, 
did circumstances permit." This method is also employed at 
Welbeck, with the greatest success. There the soil and sub- 
soil are heavy, cold, and wet ; and without some such precau- 
tion, grape-growing would be but a barren business. But by 
this method of chambering the borders, and other good manage- 
20* 



232 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

ment beside, the most abundant crops are obtained. Mr. Rob- 
erts, of Raby Castle, author of a treatise on vine culture under 
glass, and a good authority on the subject, says : — " Fault has 
been found with me for recommending heat to the roots of vines 
by fermenting manure, on account of its unsightliness ; but 
practice convinces me that without a corresponding degree of 
temperature betwixt the root and top, you cannot produce good 
grapes. I intend, however, to do away with the unsightliness 
of manure, in my new vine borders, by heating them on another 
plan." Such is the testimony of men who stand first in their 
profession, — men of undoubted probity and extensive expe- 
rience, and who, as authorities on these matters, may be fully 
relied on. No one, who once has seen the extensive gardens 
which they superintend, will dispute the propriety of the practice 
of placing fermenting manure on the surface of a vine border. 
But I must differ in my opinion from Mr. Roberts in regard to 
its effects. It may not be positively injurious, but Mr. Roberts 
has failed to prove that it is positively beneficial. Moreover, if 
he has succeeded in imparting a temperature to his vine border 
equal to the atmosphere at which he keeps his vinery, he must 
have a body of manure equal in bulk to the vinery itself. Heat 
travels with extreme slowness through the damp, confined air 
of dung-beds, and the difficulty of getting heat to travel down- 
wards is well known. A body of fermenting material may 
communicate its heat to the mere surface of the soil on which 
it lies ; but the moisture it absorbs from the atmosphere, as well 
as its saturation by rains, is communicated to the soil in place 
-of heat, so that in reality the good produced is nearly, if not 
altogether, counterbalanced by the evil. The plan Mr. R. 
intended to adopt has not, as far as I know, been made public ; 
but probably it was some kind of chambered border, with arti- 
ficial heat radiating beneath it. 

The annexed drawing represents a chambered border, heated 
with a hot-water tank, which is supplied with water from the 
pipes when it can be spared from the atmosphere of the house, 
by a tap fixed on the pipe, as shown at a, in the end section. 
If the water is allowed to flow into the tank from the boiler for 
the space of an hour, a sufficiency of heat will be communicated 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 233 

Fig. 49. ^V 




234 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

to the chamber, and the border for maintaining a perceptible 
warmth in the latter for twelve or fourteen hours. A division 
is made in the tank for the circulation and displacement of the 
water, as shown by the arrows in Fig. 49. Pigeon-hole walls 
are built across the border, about five feet distant from each 
other. Upon these rough pieces of timber are laid, as a bottom 
to the border; a layer of brush-wood (small branches) is laid 
over the timber to prevent the soil from falling through upon the 
tank. The rest should be filled, to the depth of two feet, with a 
good turfy material, with a plentiful admixture of whole bones 
and rough pieces of charcoal, to render the mass as porous as 
possible, for the admission of the heat upwards, as well as to 
maintain an equality in the moisture of the mass. Shutters are 
provided for covering the border, which may lie upon the same 
angle as the roof, or otherwise, as the front wall of the house 
corresponds to the curb in front of the border. Ventilators are 
placed in the front wall, beneath each light, for the admission 
of air into the house ; and when air is required by these front 
ventilators, the shutters covering the border must be tilted at 
the lower side, when the air passes across the border, through 
the front, into the house. We consider this mode of arrange- 
ment for the border cheaper and better than that of arching the 
chamber, as shown in Fig. 48, although both are equally effect- 
ual, and may be adopted as circumstances may suggest. 

If chambered borders be found so beneficial in England, for 
winter forcing, where the frost seldom penetrates more than a 
few inches into the ground, and rarely continues for more than 
a few days at a time, — a week or two, at the longest, — surely 
it must prove equally if not more serviceable in the New Eng- 
land states, where the winters are so intensely cold as to render 
the forcing of grape-vines at that time next to impossible. Still, 
if the forcing of this fruit can be carried on at mid-winter, at a 
reasonable cost, there is no reason to suppose that it would be 
unprofitable, even at the low prices at which grapes are usually 
sold in the principal markets of this country. All cultivators 
are aware that the profits of fruit culture are just in proportion 
to the economy with which good crops can be produced ; and 
this is more especially the case in the culture of exotic fruits, 



VARIOUS METHODS OF HEATING DESCRIBED EH DETAIL. 235 

there being more room for the exercise of skill in their produc- 
tion. 

Suppose, for instance, that we take the calculations of Mr. 
Allen, in his treatise on the Culture of the Grape-vine, where, 
in pp. 69, 70 and 71, he estimates the quantity of fermenting 
manure, necessary for the covering and warming of a border 
100 feet in length to cost S700 ; which, together with the 
other items of management, — repairs, fuel, interest on cost, 
etc., — to amount to 81120. The produce of a house so 
heated and managed, according to his calculation, is on an 
average 1067 pounds of fruit. I do not intend to dispute the 
accuracy of these calculations, although they appear startling 
enough. And doubtless Mr. Allen has had data sufficiently 
accurate and authoritative, from which to draw his deductions ; 
and hence I consider myself justified in making them partially 
the data of mine. 

And, admitting the beneficial effect of fermenting manure to 
be all that its advocates claim for it, let us compare the calcula- 
tions above, with the cost and working of chambered borders ; 
and, by balancing the two together, we shall be the better able 
to estimate the merits of each on the score of economy. 

In order to effect this, I have been at some pains to obtain the 
probable expense of such a border as that represented on page 
232. Fig. 49 ; and, in making my calculations, I have placed my 
figures rather above than under the estimate ; so that, should 
I make any error, it will be on the most favorable side. 

To make a chambered border 100 feet long, we have — 

For brick work. -$200 

Timber to form the bottom of the border, .... 60 

Tank, 50 

Extra piping for do., 10 

Extra fuel, 15 

Excavating the border. 45 

Shutters, <5cc. for covering do., 100 

Now, if we subtract 450 from 700, (the cost of manure,) we 
have a saving of 8220, the very first season ; or, in other 



236 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

words, the manure required for one year costs more than the 
making of this border, by $220. Then, if we estimate the an- 
nual expenditure on account of the border, for heating, repairs, 
etc., to be $25, we have $700, the cost of manure, minus 
$25, the cost of the tank border, which gives an annual saving 
of no less than $675 by this method of heating. 

It may be supposed that a body thus situated over a hot- 
water tank, might be too rapidly dried by the ascending heat. 
But this is only a supposition ; and in practice it amounts to 
nothing more, for the warmth generated by the tank is so grad- 
ual, and spread over so large a surface, that the heat is equally 
distributed, and no part of the mass is overheated, or one part 
heated above another. And, indeed, one would scarcely believe, 
from the small quantity of heat thus generated, that so striking 
an effect would be produced ; of course, the border must not be 
allowed to get too dry. Nor will this be a matter of so much 
difficulty as may appear, as two or three good soakings with 
water, — or, what is better, weak liquid manure, — will generally 
suffice, until the weather permits you to uncover the border 
during the middle of a wet day, covering it up again before 
evening. The operation of watering will be much facilitated 
by having a hose fitted to the tap of a cistern containing rain- 
water inside the house; and no hot-house of any kind should be 
without such an appendage. If the mechanical texture of the 
soil be good, the water soon finds its way through. The larger 
portion of the moisture being held in suspension by the lower 
stratum of soil, becomes gradually warmed by the tank, and is 
again carried upwards by the heated air ; so that the roots of 
the vines have the full advantage, not only of the heat, but of 
the moisture. The abstraction of heat may be in a great meas- 
ure prevented, in excessively frosty w T eather, by laying a few 
inches thick of straw, or stable litter, immediately over the soil 
beneath the covering. This is merely a precautionary expedient, 
and, though useful, will seldom be necessary. 

In the formation of a chambered border many alterations and 
improvements will suggest themselves to the mind of the practi- 
cal man, which could not be very conveniently represented in 
the accompanying sketches. For instance, as a covering, 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 237 

instead of shutters, I would decidedly prefer glass ; and where 
there are plenty of spare sashes about the place, they might be 
used in this way, with much advantage, just as spare sashes are 
used for covering peach and apricot wall-trees in England. But 
suppose that sashes of sufficient length were provided for the 
purpose ; the expense would probably be counterbalanced by the 
advantage gained. For a house 100 feet long, 25 sashes would 
be required, which, at 3 dollars each, would be 75 dollars; a 
very trifling sum when a desirable object is to be attained by the 
judicious expenditure of it. And, in this case, although it may 
appear injudicious to some, the object is, in my opinion, suf- 
ficiently important to justify this expense. Light absorbed is 
productive of heat, especially if the absorbing body be of a dark 
color, for then it is absorbed without being again reflected upon 
the transparent medium. Hence we see the advantage of hav- 
ing the border covered with a body admitting light; and the soil 
of which the surface of the border is composed, of a dark color, 
that the heat which falls upon it may be absorbed and retained. 

For winter forcing, small houses are decidedly preferable to 
large ones. Houses about 25 or 30 feet long are sufficiently 
large, and are more easily heated, and more convenient to man- 
age. Even in the milder climate of England, small vineries 
are preferred to large ones, and are found to be more profitably 
worked. Above all things, loftiness should be guarded against, 
as being the very worst feature in a forcing-house, as the heated 
air continues to ascend upwards; and, unless the external 
atmosphere can be admitted at the top, the vines at that portion 
of the house will always be in a state of vegetable suffocation; 
a fact of too frequent occurrence, in lofty houses, even in sum- 
mer, and which is rendered still more injurious by the present 
defective methods of ventilation. 

A few words more regarding the permanency of these borders. 
Assuming that a proper command of heat, both for the atmos- 
phere and the soil, is obtained, the question has been asked, How 
long will borders, so circumscribed, continue to supply a house of 
grape-vines with the requisite nourishment ? This question has 
hitherto proved a drawback to the adoption of these borders by 
many who have, in every other respect, the highest opinion of 



238 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

the advantages to be derived from them. In short, they are 
afraid the vines will exhaust the soil within the limits of the 
range allowed to the roots, and then fail in producing a crop for 
the want of food. Now I think a very little consideration will 
prove this to be a groundless fear. Supposing the soil to be the 
principal repository for the nutriment of the vines, and that it 
should contain all the substances in abundance, whether solid 
or gaseous, which form their structure and produce their fruit ; 
yet it is not necessary to form this border into a mass of nitro- 
geneous matter to produce these results. Plants, in this respect, 
are as bad as animals; and a vine-border may as readily be 
poisoned with excess, as impoverished for the want of proper 
elements of nutrition. Now I maintain, and I do so upon expe- 
rience, that the grand requisite to be looked to in the formation 
of a vine-border is its condition as regards texture, and not its 
chemical properties. The first secured, the latter can be added, 
not only when it is first made up, but annually afterwards, and 
each subsequent time, with as much advantage as at the begin- 
ning. The food of vines consists chiefly of the elements, car- 
bon, hydrogen, nitrogen, and oxygen, in some state of combina- 
tion, together with certain inorganic compounds, amounting to 
only about 7 per cent., as silica, salts of lime, magnesia, iron, 
potash, soda, and other bases, combined with sulphuric, phos- 
phoric, carbonic, silicic, humic, and other acids. These sub- 
stances can be supplied, in a liquid state, in quantities more than 
sufficient for the actual requirements of the vine. But their 
efficacy will very much depend upon the freeness, porosity, and 
other mechanical qualities of the soil, favorable to the decom- 
position and recombination of these elements. The general 
method of renovating a vine-border is by incorporating about 
half its bulk of manure, to the manifest destruction of many of 
the best roots, — for the best are always on the surface, — 
besides incurring a vast amount of labor and expense, which 
labor and expense would be sufficient for at least a dozen years. 
Salts of ammonia, for instance, in their various states of com- 
bination, are known to exercise a powerful influence on the 
growth of grape-vines. Now, by adding, say, 10 tons of the 
best manure to the borders, we supply them with about 85 pounds 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 239 

of ammonia, in the form of sulphate, carbonate, nitrate, and 
muriate of ammonia. Now, the same quantity will be fur- 
nished by one quarter of a ton of good Peruvian guano, at prob- 
ably one half the cost, while its application, in a liquid state, is, 
more immediately beneficial to the vines. The same salts are 
supplied. from urine, which ought to be collected in tanks for 
that purpose. By the addition of these elements, an impover- 
ished border, incapable of yielding one fifth of a crop, has been 
enriched and made to produce good crops of fruit. As I have 
said, however, I would have a border made, say, 12 or 16 feet 
wide, of good open material, not over-rich in nitrogeneous mat- 
ter, but abundantly mixed with lumps of charcoal, and plenty of 
bones; a quantity of common lime-stone (carbonate of lime) 
might be laid on the bottom, and mixed through the mass. 
With a border so formed, about 2 feet deep, and 14 feet wide, 
by the regular application of nutritious elements in a liquid 
form, and proper management in other respects, the most abun- 
dant crops may be produced, for at least a quarter of a century. 
We are well aware of the arguments that are brought to bear 
against shallow Vine-borders in this country, from their greater 
liability to become dried up by the parching droughts of sum- 
mer. But here this argument can have no application, as the 
season of forcing is at that period when the ground is saturated 
with wet, and little or no abstraction of it by the atmosphere. 
And as the temperature of any piece of ground is nearly in 
exact proportion to the amount of water it contains, so it follows 
that a vine-border saturated with water must necessarily be 
colder, and consequently more injurious to forcing plants, than 
a dry one, even without heat ! It is true, a border may be 
drained, and all superfluous and stagnant moisture carried ofF, 
but even the driest and most silicious soils have a certain 
capacity of suspending moisture in their pores, and as this 
capacity is greater in soils containing much organic matter than 
in those of a more sandy nature, it follows theoretically, — and 
we find it so in practice, — that rich borders are colder and 
wetter than the common garden soil. I believe this is a fact 
which no one will dispute. But however warm vine-borders 
may be by their natural position, or rendered so by artificial 
21 



240 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL, 

drainage, they must still be very far from the internal tempera- 
ture of the house, — a fact which requires no calculation to 
prove it. And hence, although the vine, of all other fruit-bear- 
ing plants, will accommodate itself to circumstances apparently 
the most unpropitious, and will stand forcing in mid-winter bet- 
ter than any other fruit we can place into a hot-house, still, it 
cannot be expected that we shall arrive at anything like perfec- 
tion in its produce by winter-forcing, under the present methods 
of cultivation. And we know that, whatever can be said in 
favor of carrion-borders, no mere aggregation of organic matter 
will suffice for the production of grapes, especially in winter, 
if the principle of life be impotent, and the functions of the plant 
impaired, whether by natural or artificial causes ; and nothing 
is more likely to weaken the one, or impair the other, than 
placing the roots of vines in an ice-house, and the branches in 
an oven. 

In close connection with the foregoing subject is a system 
which has engaged no inconsiderable share of attention in Eng- 
land, and may probably be employed with equal advantage in 
this country. The system to which I allude, is forcing by hot 
walls covered with glass. It has now become common to build 
garden walls hollow, and heat them with hot water, with flues, 
or both, and by covering them with temporary roofs, consisting 
either of spare sashes on hand, or by having sashes made for 
the purpose. By this means, a range of portable houses may 
be constructed upon any walls adapted for that purpose, at a 
very inconsiderable expense, compared with that of permanent 
houses. — (See Part I. Construction of Walls.) 

Fig. 50 shows an end section of the wall ; a a, ties across the 
wall, at regular distances, for the purpose of strengthening the 
fabric ; b, the pipes for hot water, or the situation of the flue, if 
that method of heating be adopted; c, the furnace and boiler, 
placed in a recess of the wall, as shown in the ground plan ; d 
d, the returning pipes, or the position of the returning flue, if 
pipes are not used ; e, the projecting support for the sashes 
under the coping; /, the lower supports for the sashes, consist- 
ing of timber posts driven into the ground, that no obstruction 
may be presented to the roots of the vines by a brick wall ; g, 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 241 

Wm. 50. 




- mmmM/mm^Mmfm ^. 






~~ 






Y///M/////////A 



w, 



I_~ 



I 









242 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

the sashes ; h h k, are square tubes of wood, penetrating the 
soil to the chamber beneath, to let the heat rise up into the 
space confined within the sashes and the wall ; the number of 
these openings depending entirely upon the weather, and the 
season of forcing. They may be closed with a lid when the 
sashes are removed. From the foregoing description, it will be 
perceived that an erection of this kind has all the advantages 
of a house, — at least as far as grape-growing is concerned, — 
without the consequent expense, and when once all the mate- 
rials are properly adjusted, they can be removed, or replaced, by 
almost any gardener, without the aid of a tradesman. The 
rafters are merely fastened to a plate of wood, about one foot 
broad, and two inches thick, by means of iron pegs, as at e, 
in the end section, and also at the bottom to another plate, sim- 
ilar to the one above, and fitted into the posts at f; the sashes 
are fixed to the rafters by means of a latch, or thumb-screw, 
placed within reach of the operator, for the facility of admitting 
air. This is effected by letting down the sashes to any distance, 
and supporting them by notched brackets, or letting them down 
to the ground, if necessary, as shown by the dotted line, at /. 

This method may be adopted without having any cavity 
beneath the border, and, of course, will be cheaper, although we 
would decidedly prefer such a cavity, did circumstances permit. 
The advantage of hollow walls, warmed by some method, has 
been long well known to gardeners, and so highly are they 
thought of in England, that scarcely any garden of consequence 
is without them. Indeed, in the majority of seasons, the culture 
of the vine, peach, nectarine, apricot, and fig, — even on walls, — 
would be a very precarious and uncertain business, although 
the method of covering such walls with portable glass has but 
very lately been brought into use, and, now that glass is cheaper 
in that country, is almost certain to be extensively applied to 
this purpose. In one or two cases we have seen this method 
adopted with astonishing success, and without any cavity, or 
any other preparation than the common border and wall of the 
garden. In one place we had forty feet of a wall thus covered 
with spare sashes ; the space included some peach and fig 
trees, in excellent bearing condition, and well set with buds, 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 243 

giving promise of a fair crop. The wall was covered with the 
glass on the first of February, but no heat was applied to the 
wall until the beginning of March. The sashes were fixed 
exactly as we have described in the foregoing sketch. The wall 
and fire-place were precisely the same, but no cavity was be- 
neath the border. The result was, that the crop ripened five 
weeks earlier than those on the same wall, uncovered, without 
heat, and nearly four weeks earlier than those on the same wall, 
with heat, and covered, in the usual way, with netting. Now 
this was merely an experimental result, without much previous 
preparation, save the covering up of the wall a month earlier 
than the warming commenced, — if, indeed, this can be called a 
preparation, — being an absolutely necessary prerequisite to suc- 
cess, under any method of forcing. When the warm weather 
set in, the sashes and rafters were taken away, and the enclosed 
part received, during the season, the same treatment as the 
other portions of the wall. 

In forming a hollow wall, there will be quite as much saved 
by the internal cavity as will suffice to warm it, as only about 
one half the quantity of bricks are required ; and even without 
a heating apparatus, hollow walls are superior to solid ones, for 
horticultural purposes ; for, under all circumstances, they are 
found to be both warmer and drier. The addition of a heating 
apparatus, however, will render the wall a very useful auxiliary 
to the forcing-house, and the cost will be amply compensated by 
the utility. By looking at the foregoing plan, it will be seen 
that the furnace is placed in the foundation of the wall, with a 
few steps to descend to it, the whole being covered with a trap- 
door, leaving nothing unsightly open to the view of the visitor. 

In many parts of this country, grapes are frequently overtaken 
by the autumn frosts, before they are ripened, and in many 
others, they do not ripen at all. Now, it is obvious 3 that it is 
neither owing to a deficiency of sun-light, nor a deficiency of 
heat, for in Britain the quantity of both are much less, and the 
quality of the latter less powerful for the maturation of fibre and 
fruit ; and yet it is common enough to have good crops of (what 
in America are called foreign) grapes, on the open walls. In 
ordinary seasons, the black Hamburg, Muscadine, and Fron- 
21* 



244 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 

tignacs, ripen well in the open air, on southern aspects ; and in 
all seasons they succeed in ripening their fruit, in tolerable per- 
fection, on hollow walls, with a little heat in spring, if the 
season be backward, and a little in autumn, if the season 
be late, i. e., if cold weather should set in unusually early, 
which it frequently does in Scotland ; and yet we have seen tol- 
erable crops of grapes produced north of the Tweed, on heated 
walls, without any glass at all. This statement may be received 
with incredulity by some, who have had poor success in the 
cultivation of foreign grapes, in the open air, in this country, 
under circumstances of climate unquestionably more favorable 
than can be found in any part of the British Islands. We believe 
this statement will be corroborated by the testimony of every 
one who is acquainted with the nature of the climate of both 
countries. In fact, so much are people in this country impressed 
with the unfavorable nature of an English summer, that in all 
journals, magazines, periodicals, and papers, of every descrip- 
tion, we, without one single exception, find it qualified with the 
words, dull, gloomy, austere, wet, cold, damp, dripping, and 
many other appellations of similar import, which it is not my 
present purpose either to confirm or confute. But as there has 
not, as yet, been (as far as we can learn) any general cause 
assigned for the general failure here, there is but one infer- 
ence that can be drawn from the above statements, viz., that 
there must be, in this country, something wrong, or something 
wanting, in the modes of cultivating foreign grapes, in the open 
air. It cannot be said that the summers are too hot for the 
grape-vine ; for there is hardly another plant in the vegetable 
kingdom, that will bear a greater amount of natural or artificial 
heat, or greater alternations of heat and cold, under circum- 
stances otherwise favorable. There is no degree of heat, to 
which natural vegetation is subjected in this country, under 
which it will not flourish, provided the intense rays of the noon- 
day sun be not concentrated upon its foliage ; and it is a well- 
known fact, that grape-vines will not produce fruit abundantly 
when they are not in a favorable aspect. There can be little 
doubt that we must look to the condition of the plant, during 
the spring and autumn, to enable us to reach the cause, and 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 245 

this appears to be substantially proved, by the invariable success 
that has attended the culture of foreign grapes in cold houses, as 
well as other facts suggested by experience, in the culture of 
that noble fruit. The value and importance of the grape-vine 
have already induced me to dwell longer on this subject, in con- 
nection with heating, than I intended ; I therefore consider it 
foreign to my subject to enlarge further on its culture, although 
there is great room for speculation, theory, experiment, and 
practical improvement. Indeed, it would be difficult for the 
practical horticulturist to take hold of a subject affording a wider 
field for successful experiment, and holding out brighter hopes 
of beneficial results. 

Before concluding this chapter on heating, I will briefly notice 
another system, more, however, on account of its novelty, than 
applicability to the warming of hot-houses, although it has, in 
some instances, been applied to this purpose. I refer to the 
method of heating, by which the hot air is carried along by the 
power of a steam-engine. This system is applied to the warm- 
ing of large factories in England, and has been also applied, with 
apparent success, in some large nursery gardens, in Germany. 
The following description is from the pen of Mr. Marnock, the 
able editor of the " Gardener's Journal," (Eng.,) and drawn from 
his own observations of the apparatus, while visiting the gardens 
of Baron Hugel, near Schonbrunn, where the system was in 
operation at the time. 

" The most remarkable feature about this garden is the mode 
of heating, which we shall now attempt to describe. In the 
first place, there is a large fire-place constructed ; through this 
fire-place two or more pipes are introduced ; the pipes are of cast- 
iron ; one end of these pipes communicates with the common 
atmosphere, the opposite end being introduced into a large box, 
or flue ; in this flue is placed a fan, driven by a steam-engine, 
which fan is made to revolve in this air-flue, at a short distance 
from the fire-place. It will readily be understood, that, when 
the fire is in action, with those iron pipes passing through it, 
and terminating in the large air-flue, the revolving action of 
the fan, in a direction to draw the common atmospheric air 
through the iron pipes in the fire-place, will also force the heated 



246 VARIOUS METHODS OF HEATLXG DESCRIBED IN DETAIL. 

air onwards to the other end of the flue, and thence through tin, 
zinc, or any other kind of pipe placed there to convey it away. 
By these means it is conducted (i. e., the heated air from the 
box) into the different stoves and green-houses. Each house, 
or, rather, each compartment, is provided with a supply-pipe and 
a tap, by which heated air is admitted by measure, and of course 
regulated according to the requirements of the plants. We 
could not clearly ascertain the exact size of the fire-place, but 
we saw some iron pipes, which we were told were similar to 
those in use in the fire-place for heating the air, and we sup- 
posed them to be about six inches in diameter. These pipes, 
as they are exposed to the action of a strong fire, become greatly 
heated, and the air, in passing through them, becomes intensely 
hot and dry, consequently, deprived of its oxygen and aqueous 
properties. Here, however, no evaporating pans are used for 
moistening the warm air, as in common hot-air furnaces, and 
the method adopted for supplying the heated air with moisture 
is quite as novel as the system itself. To effect this, a steam 
jet is played into the hot-air flue, immediately before it enters the 
different compartments, and Mr. Hooibrink, the gardener to 
Baron Hugel, stated that he admitted the steam according to 
the nature of the plants cultivated in each apartment. Thus, 
he allowed so many feet of steam for his orchards ; so many for 
his stove plants, and so many for his common green-house 
plants ; thus each kind of plants is supplied with steam, 
according as it requires a moist or dry atmosphere. 

11 Thus, if we are rightly understood, there is, first, a large fire- 
place ; through this fire two or more cast-iron pipes, six inches 
in diameter, are passed ; they are so placed as to be subjected to 
the most intense action of the caloric produced by combustion ; 
one end of these pipes is exposed to the external atmosphere, 
the other ends enter a large oblong box, on a level with the 
pipes, in which is placed a fan, similar to those used in small 
fanning mills. This fan is made to revolve with considerable 
rapidity, by the power of a small steam-engine, drawing the 
atmospheric air inwards through the tubes exposed to the fire, 
and forcing it onwards through the main conductor, and thence 
into the smaller tubes leading to the right or left, up or down, 



VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 247 

as the case may be, for the supply of the mansion, and the 
several hot-houses, all of which are heated by the same appara- 
tus. Here the air is moved and replaced, not only by its own 
density, as in the common methods of hot-air heating, but it is 
drawn rapidly inwards by the suction of the fan on the one side, 
and driven onward by its propulsive power on the other ; and 
thus it appears the heat travels with great rapidity, and within 
a few minutes after the heated air is turned on the apartment, 
and moistened as may be desired by the jet of steam already 
described."^ 

* Fans are now frequently employed for effecting ventilation, and 
are generally connected with the heating apparatus. They have never, 
as far as we know, been employed for this purpose in any kind of hor- 
ticultural structures, although we can see no reason why they should 
not be so. This will be again referred to^ when we come to treat on 
that part of our subject. 



PART III. VENTILATION. 



SECTION I. 

PRINCIPLES OF VENTILATION. 

1. The ventilation of hot-houses, either in summer or win- 
ter, constitutes an important, if not the most important, item of 
their general management, as it bears more directly upon the 
condition of the external and the internal atmosphere. It re- 
quires, therefore, the strictest attention of the gardener at all 
seasons of the year. For, important as other things connected 
with exotic horticulture may be, — light, for instance, — it is, 
nevertheless, more under the gardener's control, and more sub- 
ject to his will. He places his plants within a transparent 
medium, which is, in its general surface, impermeable to the 
atmospheric air; and he forms for them an artificial atmos- 
phere, which is invigorating, or the reverse, according to his 
knowledge of the laws that regulate the atmosphere, or the 
general principles of aerometry. Notwithstanding the many 
discoveries that have been made regarding the properties of air, 
I have been unable to find any work bringing these discoveries 
to bear upon the airing of hot-houses. It is true this must be 
accomplished by the " practical " man, and the sooner we begin 
to think about it the better. Every horticulturalist, no matter 
what his department in the vineyard may be, soon discovers the 
necessity of maintaining a continual warfare with its different 
conditions of purity and impurity, its aridity, and its moisture. 
We have, indeed, various theories propounded by physiologists, 
regarding the power of plants to withstand these vicissitudes, 
some of which have their general principles as yet enveloped in 
a mist of shadowy vagueness. 

Many remarkable facts, however, might be mentioned relative 



PRINCIPLES OF VENTILATION. 249 

to the qualities and quantities of certain atmospheric elements 
which plants are capable of sustaining in deficiency or in excess. 
And the one or the other of these conditions appears to some of 
the species a natural and even a necessary circumstance. The 
degree in which vitality is sometimes retained by plants, under 
the most unfavorable conditions, for a period to which it is diffi- 
cult to assign a limit, is one of the most interesting and curious 
circumstances in their economy. Instances have been related 
of the growth of bulbs, unrolled from among the bandages of 
Egyptian mummies. Although there is good reason to believe 
that deception has been practised on this point, upon the credu- 
lity of travellers, still there is nothing impossible in the asserted 
fact. Light, heat, and moisture are the cause of the development 
of these curious structures, and their forms become expanded 
under the additional agency of atmospheric air. Now, when 
removed from the influence of these, there is no reason why a 
bulb, if it can remain unchanged for ten years, should not do so 
for a hundred ; and if for a hundred, why not for one thousand 
years ? The vitality of seeds under similar circumstances 
appears quite unlimited. * 

In the first chapter of this treatise, we have ventured to assert 
that light is of more importance to plants than air, although we 
are aware that this point is open to much discussion, from the 
fact of some plants being adapted to thrive under the almost 
total deprivation of it. These, however, will generally, if not 
solely, be found to consist of plants in the lowest orders of 
organization, such, for instance, as the algee, some of which, pos- 
sessing a bright green color, have been drawn up from the depth 
of more than one hundred fathoms, to which the sun's rays can- 
not penetrate in any appreciable proportion ; and also the fungi, 
which have been found growing in caverns and mines to which 
no rays from the sun, either direct or reflected, would seem to 
have access. These facts, however, do not greatly affect the 

* Melon seeds have been known to grow at the age of 40 years, kid- 
ney beans at 100, sensitive plant at 60, rye at 40, and there are now 
growing, in the garden of the Horticultural Society, raspberry plants 
raised from seeds 1600 or 1700 years old. — [Lindley's Introduction to 
Botany.] 



PRINCIPLES OF VENTILATION. 

accuracy of our assertion, for we find that all the highly devel- 
oped organisms, such as we cultivate in our hot-houses, are only 
adapted to exist where they can be daily invigorated by the 
sun's rays. This fact is very strikingly illustrated in the effect 
produced on tropical plants growing in hot-houses in the north- 
ern latitudes, where, deprived of the intensity of the sun's rays, 
under which they naturally luxuriate, they seem completely 
changed by the long absence of the luminary on whose cheering 
influence they depend. In such cases, no quantity or quality 
of air will compensate for the loss of the sun's vivifying beams. 
In the management of hot-house plants, the attentive ob- 
server cannot fail to perceive the remarkable effects produced 
upon certain kinds of plants by the circumstances in which they 
are placed, as to heat, light, and air; and hence the propriety of 
arranging plants in hot-houses, not merely according to their 
heights and colors, but also according to their habits and 
requirements in relation to these elements.^ Some plants will 
endure an intensity of solar light, without injury, which would 
utterly paralyze and suspend the functions of others; some will 
luxuriate in an arid temperature, in which others would be 
destroyed, and some require daily supplies of fresh air, while 
others will exist even in a healthy state for years where the 
atmospheric air is, one would think, almost excluded. Even 
in nature there are many striking exemplifications of these 
facts. A hot spring in Manilla islands, which raises the ther- 
mometer to 187°, has plants flourishing in it and on its bor- 
ders. In hot springs near a river of Louisiana, the tempera- 
ture of which is from 122° to 146°, have been seen growing, not 
merely the lower and simpler plants, but shrubs and trees. In 
one of the Geysers of Iceland, which was hot enough to boil an 

* For example, the common weeds, called chickweed, groundsel and 
Poa annua., evidently grow at a temperature very near that of 32°, 
while the nettles, and mallows, and other weeds around them, remain 
torpid. In like manner, while our native trees are suited to bear the 
low temperature of an English summer, and, in most cases, suffer 
if removed into a warmer country, such plants as the mango and coffee- 
tree, etc., inhabitants of tropical countries, soon perish, even in our 
warmest weather, if exposed to the open air. — [Lind. The. of Hort.] 



PRINCIPLES OF VE:rr:LA7 :v.\ 251 

egr/ in four minutes, a . of chara has been found growing 

and reproducing itself; and r< of an humble kind has 

rred in the similar boilii of Arabia, and file 

Cape of Good Hope. One of the most remarkable fact-, on 
. in reference to the power r ' %e\x tion to proceed tmdex 

. temperature, is related by S - r / Staunton, in his as 
of Lord M y to China. At the island of 

found, the rnud of which was far hot- 
ter tha rth to a species oi liverwort. 
A large squill bulb, which it was wished to dry and prej 
has boon known to push up its stalk and loaves, when buried in 
sand kept up to a r. tceeding that of boiling 
water. 

iwenred :. a ita exceedingly tenacious of life 
under the deleterious influences of arbonk acid., sulphur 
chlorine and other gases. We hai e eea : - number of d if:'-- 
kino 1 -. placed in a close .' i e, and fumigated with sul- 

phure -;d. though 

uninjured. This fact fa - 
many in the fumigating of theii ;•-.-..-. vithtobaccc when 

. ;er sorts would be sensibly injured by *;. e 
while thougn receivi ig a much larger portion, bore it 

with impunity. 

It is evident, however, that though many plants will live for 
Mi time under these circumstances, a 
the a* amount of light and hv 

v. v to the pe: of their functions, and the perfeo 

.:' their flowers and fruit The fact is well known, that if 
we take a healthy planl from the light a ■;■■•■•.--. -.-:.-.,: a.-.-J 

place it in the roc lse, it will become sickly, 

and ultimately bag -..-.- ; if it be placed in a dark, cold 

cellar, its death will be more speedily produced. In like man- 
ner, roses grown in a forcing-house in winter are less fra; 
than those gro sunshine ■/. i lmmer. J.-, gen- 

eral, plants grown . months form seore* 

active, in erery iea pect than die ss ante grown ia a 

hot-house, unde nnter; and even 

finest forced fruits and regetahle* this is perceptibly the case. 
22 



252 PRINCIPLES OF VENTILATION. 

2. Much discussion has taken place upon the question 
whether or not vegetation is, upon the whole, serviceable in puri- 
fying the atmosphere ; that is, whether plants give out most car- 
bonic acid or most oxygen. Priestley maintained that the latter 
was the only effect of vegetation, arid that plants and animals 
are thus constantly effecting changes in the atmosphere which 
counterbalance one another. Subsequent experiments seem to 
show, however, that the carbonic acid given out during the 
night, equals or even exceeds in amount the oxygen given out 
by day. Bat this might be owing to the employment of plants 
which had become weak and unhealthy, by being kept in an 
impure atmosphere, previous to being experimented on, and 
which had not been exposed to a fair degree of light. Dr. Dau- 
beny, of Oxford, has recently shown that, in fine weather, a 
plant, consisting chiefly of leaves and stems, if confined in a 
capacious vessel, and duly supplied with carbonic acid during 
sunshine, as fast as it removes it, will go on adding to the pro- 
portion of oxygen present so long as it continues healthy; 
the slight diminution of oxygen and increase of carbonic acid 
which take place during the night bearing no considerable pro- 
portion to the degree in which the contrary effect occurs during 
the day.^ 

Thus we see that the two great organized kingdoms of 
nature are made to cooperate in the execution of the same 
design, each ministering to the other, and preserving that due 
balance in the constitution of the atmosphere, which adapts it 
to the welfare and activity of every order of beings, and which 
is quickly destroyed when the operations of any of them become 

* Plants decompose carbonic acid during the day, and form it again 
during the night, — the oxygen they inhale at that time entering again 
into combination with their carbon, — and, during the healthy state of a 
plant, the decomposition by day, and recomposition by night, of this 
gaseous matter, are perpetually going on. The quantity of carbonic acid 
decomposed is in proportion to the intensity of the light which strikes a 
leaf, the smallest amount being in shady places ; and the healthiness of 
a plant is cateris paribus in proportion to the quantity of carbonic acid 
decomposed. Therefore, the healthiness of a plant should be in propor- 
tion to the quantity of light it receives by day. — [Lind. The. of Hort.] 



PRINCIPLES OF VENTILATION. 253 

suspended, as is the case in the artificial atmosphere of a hot- 
house. And as by artificial means the balance is therein 
destroyed, so, also, by artificial means must the elements of the 
atmosphere be adjusted, and the balance maintained. 

It is impossible for us to contemplate so special an adjustment 
of opposite effects, without admiring this beautiful dispensation 
of Providence, extending over so vast a scale of being, and 
demonstrating the unity of the plan upon which the whole sys- 
tem of the organized creation is designed. And yet man, in 
his ignorance, has done his utmost to destroy this beautiful and 
harmonious plan. It was evidently the intention of the Creator, 
that animal and vegetable life should everywhere exist together, 
so that the baneful influence which the former is constantly 
exercising upon the air should be counteracted by the latter. 
Nothing, therefore, can be more prejudicial to the health of a 
large population, than the close packing of houses together, as 
presented in large cities. Hundreds of thousands of men, with 
manufactories of all kinds, — the smoke and vapors of which are 
still more injurious than the foul air produced by human respi- 
ration, — being crowded together in the smallest possible com- 
pass, with scarcely the intervention of an open space on which the 
light and air of heaven may freely play, and without any oppor- 
tunity for the growth of any kind of vegetation sufficiently luxu- 
riant to give pleasure to the eye, or sufficiently energetic to 
answer its natural purpose ; for the close confined atmosphere 
of crowded cities is almost as injurious to vegetation as to ani- 
mals ; the smoke, which is constantly hovering above them 
prevents their enjoyment of the clear bright sunshine which 
they require for their health, and the dust, which is constantly 
floating in the atmosphere, covers the surface of their leaves, 
clogs up the pores, and prevents respiration. 

This is the reason why plants thrive so badly in dwelling- 
houses in large cities, and also in the external air in the streets 
and squares. But lofty trees are so beneficial in such situations 
that they have with truth been called the lungs of large cities, 
so important is the effect produced by them in purifying the air. 
It is true, they may occasion some degree of dampness in the 
immediate neighborhood, but this evil is more than counterbal- 



254 PRINCIPLES OF VENTILATION. 

anced by the good they effect. " New Haven," justly called the 
City of Elms, is almost embowered in the shade of lofty trees, 
and is remarkable for the salubrity of its atmosphere, and the 
health of its inhabitants. There, almost every house has its 
garden ; and the daily consumers of its deleterious exhalations 
stand in the open streets, at once the ornaments of the city and 
the scavengers of the air. The cutting down of a healthy tree, 
in the midst of a large town, without some very strong reason, 
should be regarded as an offence to the community, and an 
injury to the public weal. It is much to be wished that other 
towns, that are rapidly increasing in extent and population, 
would follow the example of New Haven, and bad ventilation 
and impure air would, in a very great degree, be deprived of 
their injurious effects. 

2. Under favorable circumstances, plants are able to appropriate 
a larger amount of carbonic acid than that commonly existing 
in the atmosphere. The vegetation around the springs, in the 
valley of Gottingen, which abound in carbonic acid, is very rich 
and luxuriant, appearing several weeks earlier in spring, and 
continuing much later in autumn, than at other spots in the 
same district. But it is probable that, taking the average of the 
whole globe, and at all seasons, the quantity of carbonic acid 
existing in the air is that most adapted to maintain the health 
of the plants at present inhabitants on its surface, as well as to 
interfere as little as possible with the animal creation. In hot- 
houses, however, the case is different, especially in winter ; for, 
although carbonic acid be not produced by the respiration of 
animals, it is produced in abundance by other causes, and these 
same causes also depriving the atmosphere of oxygen and its 
aqueous vapor, the carbonic remains in excess, and its effect 
upon the plants is easily perceived. The presence of oxygen, 
in proper quantity, in the atmosphere of a green-house, or hot- 
house of any kind, is even more necessary to be artificially 
maintained, than carbonic acid, because the oxygen affords the 
means by which the superfluous carbon is removed. We know 
that plants in a hot-house suffer more frequently from an excess 
of carbon than an excess of oxygen, arising from the causes 



PRINCIPLES OF VENTILATION. 



255 



above stated. It has been calculated that hot-houses, during the 
application of fire heat, contain four times as much carbonic 
acid in their atmosphere as is necessary for the health of the 
plants. 

" Charcoal possesses the property of absorbing some gases to a 
great extent, as may be seen by the following table, in which 
the numbers indicate the volumes of gases absorbed, that of the 
charcoal being taken as unity.^ 

Absorption of Gases by Charcoal. 



Ammonia, 90 

Muriatic acid, 85 

Sulphureous acid, 65 

Sulphuretted hydrogen, . ... 55 

Nitrous oxide, 40 

Carbonic acid, 35 



Bi-carb. hydrogen, 35 

Carbonic oxide, ....... 9.4 

Oxygen, . . . 9.2 

Nitrogen, . . 7.5 

Carbur. hydrogen, 5 

Hydrogen, 1.7" 



The above table will show how very useful charcoal may be 
rendered as an agent in the absorption of these gases, when 
present in excess, either in a plant-house or other places. 

3. The evolution of heat by plants is most evident at those 
periods of their existence in which an extraordinary quantity of 
carbonic acid is formed and given off. This is the case during 
the germination of seeds ; and though the heat produced by a 
single seed is too soon carried off by surrounding bodies to be 
perceptible, it accumulates to a high degree, where a number 
are brought together, as in the process of malting, when the 
thermometer has been seen to rise 110°. An extraordinary 
amount of carbonic acid has been found to accumulate in a hot- 
house, in one night, so as sensibly to affect the respiration of in- 
dividuals entering the house in the morning ; which shows the 
necessity of night ventilation. The disengagement of carbonic 
acid has been sensibly found in some plants, by the evolution 
of heat in some of their organs. Thus, the flower of a gera- 
nium has been found to possess a heat of 87°, when the air 
around it was 81°. As in the case of seeds, however, the pro- 
duction of heat is most sensible where the flowers are crowded 
together, and in those flowers where the size of the fleshy disk is 



22# * Daniel's Introduction to Chemistry, 



256 PRINCIPLES OF VENTILATION. 

most considerable, the quantity of carbon to be united with the 
oxygen is consequently the greatest. And the combination of 
this cause with the other, causes the temperature of the clus- 
ters to be raised very high. A thermometer placed in the 
centre of five spadices has been seen to rise to 111 , and one in 
the centre of twelve, to 121°, while the temperature of the ex- 
ternal one was only 66°. 

From what has been stated, we think it may be argued that 
plant-houses require to be ventilated at night even more than 
during the day ; but the quantity of air then admitted must 
be in proportion to the mean of the internal and external 
temperatures; but more particularly depending on the con- 
dition of the plants. 

4. Various theories have been propounded by physiologists 
regarding the power of plants to withstand vicissitudes of tem- 
perature, and, among others, we have the following from the high 
authority of Decandolle : — 

First, in the inverse ratio of the quantity of water they con- 
tain ; secondly, in proportion to the viscidity of their fluids ; 
thirdly, in the inverse ratio of the rapidity with which the fluids 
circulate ; fourthly, in proportion to the size of the cells, so is 
the liability of the plants to freeze ; fifthly, the power of plants 
to resist the extremes of temperature is in exact proportion to 
the amount of confined air which the structure of the plants 
enables them to contain. These and other principles are laid 
down, and, apart from their practical observation, they are of 
themselves sufficient to form the ground, of theory. There is 
nothing, however, in the above calculated to be of material ser- 
vice to the gardener in the culture of exotic plants. The dis- 
tinctions upon which rest their powers to resist changes of tem- 
perature are by far too undefined and minute to enable us to 
determine the quantity or quality of the organic elements they 
contain. Neither can we ascertain the dimensions of the cells 
with sufficient accuracy to determine the precise degree of heat 
or cold which any given plant will endure. In the management 
of tender plants, we must find a firmer foundation on which to 
rest our principles of action. We must endeavor to ground our 



PRINCIPLES OF VENTILATION. 257 

judgment upon broader and safer principles ; and, in order to 
reach this point, let us briefly consider the nature of atmospheric 
action upon hot-houses. 

Before entering upon any illustration of its practical effects 
upon these structures, we will give an extract from Dal- 
ton's Chemical Philosophy, which will enable us to account 
more clearly for some of those results that we have often 
observed, and which have so often humiliated our practical pride 
and baffled all our boasted experience. In fact, they have been 
considered as belonging to that class of unaccountabilities which 
our Creator has placed beyond the ken of human discovery. 

" It is a remarkable fact," Dalton observes, " and has never I 
believe been fully or satisfactorily accounted for, that the atmos- 
phere, in all places and seasons, has been found to decrease in 
temperature as we ascend, and nearly in arithmetical progression. 
Sometimes this fact may have been otherwise, i. e., that the air 
was colder at the surface of the earth than above ; particularly at 
the breaking up of a frost, I have observed it so. But this is evi- 
dently the effect of a great and extra ordinary commotion in the 
atmosphere, and is generally of very short duration. What, 
then, is the occasion of this diminution of temperature in ascend- 
ing ? Before this question can be solved, it may be necessary 
to consider the defects of the common solution. Air, it is said, 
is not heated by the direct rays of the sun, which passes through 
it as a transparent medium, without producing any calorific 
effect till they reach the surface of the earth. The earth, being 
heated, communicates a portion to the atmosphere, while the 
upper strata, in proportion as they are more remote, receive less 
heat, forming a gradation of temperature similar to what takes 
place along a bar of iron, when one of its ends is heated." The 
first part of the above solution is probably correct. Air, it would 
seem, is singular in regard to heat ; it neither receives nor dis- 
charges it, in a radiant state. If so, the propagation of heat 
through air must be opposed by its conducting power, the same 
as in water. Now, we know that heat, applied to the under sur- 
face of a column of water, is propagated upward with great 
velocity, by the actual ascent of the heated particles ; it is equally 
certain that heated air ascends in the same way. From these 



258 PRINCIPLES OF VENTILATION. 

observations, it would follow that the causes assigned above for 
the gradual changes of temperature in a perpendicular column 
of atmosphere, would apply to a state of temperature the very 
reverse of the fact ; namely, that the higher the ascent, or the 
more distant from the earth, the higher would be the tempera- 
ture. Whether this reasoning be correct, or not, we think it must 
be universally allowed that the fact has not hitherto received a 
very satisfactory explanation. We conceive it to be one involv- 
ing a new principle of heat ; by which we mean, a principle 
which no other phenomenon of nature presents us with, and 
which is not at present recognized as such. We shall endeavor, 
in what follows, to make out that principle. 

The principle is this. The natural equilibrium of heat, in an 
atmosphere, is when each atom of air, in the same perpendicular 
column, is possessed of the same quantity of heat ; and, conse- 
quently, the natural equilibrium of heat in an atmosphere is 
when the temperature gradually diminishes in ascending. That 
this is a just consequence cannot be denied, when we consider 
that air increases, in its capacity for heat, by rarefaction ; and, 
therefore, if the quantity of air be limited, it must be regulated 
by the density. It is an established principle, that every body 
on the surface of the earth, unequally heated, is observed con- 
stantly to tend towards an equality. The new principle an- 
nounced above would seem to suggest an exception to this law ; 
but if it be thoroughly examined, it can scarcely appear in that 
light. Equality of heat and equality of temperature, when 
applied to the same body, in the same state, are found to be so 
uniformly associated together, that we scarcely think of making 
any distinction between the two expressions. No one would 
object to the commonly observed law being expressed in these 
terms. When any body is equally heated, the equilibrium is 
found to be restored, when each particle of the body becomes 
possessed of the same quantity of heat. Now the law, thus 
expressed, is what I apprehend to be the true general law, which 
applies to the atmosphere as well as to other bodies. It is an 
equality of heat, and not an equality of temperature, that nature 
tends to restore. 

The atmosphere, indeed, presents to us a strikingly peculiar 



PRINCIPLES OF VENTILATION. 259 

feature, in its regard to heat. We see, in a perpendicular col- 
umn of air, a body without any change of form, slowly and 
gradually changing its capacity for heat, from a less to a greater ; 
but all other bodies retain a uniform capacity throughout their 
substance. If it be asked why an equilibrium of heat should 
turn upon the quality in quantity, rather than in temperature, I 
answer, I do not know ; but I rest the proof of it upon the fact 
of the inequality of temperature observed in the atmosphere in 
ascending, which invariably becomes colder as we ascend in 
height ; while, in artificial atmospheres, as in the case of a hot- 
house, the fact is quite the reverse. If the natural tendency of 
air was to an equality of temperature, there does not appear to 
me any reason why the lower regions of air are warmer than 
the higher, or why the law of equalization held good in one case 
and not in another. 

To enable us to apply these arguments more clearly to our 
subject, it will be necessary more fully to consider the relation 
of the atmosphere in regard to heat; and the arguments already 
advanced in behalf of the principle we are endeavoring to estab- 
lish, are powerfully corroborated by the following facts. 

We find, by the observations of Bougeur, Sassure, and Gay 
Lussac, that the temperature of the atmosphere, at an elevation 
where the weight is half that at the surface, (about 14,000 feet, 
or less than three miles,) is reduced in temperature 50° Fahren- 
heit; and, from experiment, it appears that air, suddenly rarefied 
from two to one, produces 50° of cold. Hence we might infer 
that the stratum of air at the earth's surface being taken up to 
the height above mentioned, preserving its original temperature 
and suffered to expand, becomes two measures, and is reduced to 
the temperature of the surrounding air, and vice versa. In like 
manner, we may infer, if a column of air from the higher strata 
of the atmosphere were condensed and brought into a horizon- 
tal position on the earth's surface, it would become of the same 
density and temperature as the air around it, without receiving 
or parting with any heat whatever. Another important argu- 
ment in favor of the theory here advanced, may be derived from 
the contemplation of an atmosphere of vapor. Suppose the pres- 
ent aerial atmosphere were to be substituted for one of aqueous 



260 PRINCIPLES OF VENTILATION. 

vapor; and suppose, further, that the temperature of the earth's 
surface were uniformly 212°, and its weight equal to 30 inches 
of mercury. Now, at the elevation of about six miles, the 
weight would be fifteen inches, or one half of that below ; at 
twelve miles, it would be 7£ inches, or one fourth of that at the 
surface, and the temperature would probably diminish 25° at 
each of these intervals. It could not diminish more ; for the 
diminution of temperature 25° reduces the force of vapor one 
half. If, therefore, a greater reduction of temperature were to 
take place, the weight of the incumbent atmosphere would in- 
crease, being converted into water, and the general equilibrium 
would thus be disturbed by condensation in the upper regions." 
It has been observed, that if the ventilators of hot-houses be 
kept close during the day, the internal temperature will rise, 
although no artificial heat be applied ; from which it has been 
supposed that glass freely admits the calorific rays to pass 
through it, in their descent, but arrests it in their upward progress. 
Professor Robinson has proved that glass freely transmits the 
luminous rays, but stops the calorific rays, till it becomes satu- 
rated with heat to a certain degree ; which proves, also, that 
light and heat are not identical, although both obey the same 
laws of reflection, refraction, and radiation. Although heat may 
arise from the same source as light, and possess a great affinity 
to it, yet caloric possesses properties peculiar to itself, and differs 
in its degree of affinity for other bodies ; for, although it has a 
tendency to come to an equilibrium, when bodies differing in 
quality are exposed to its influence, it has been found that 
these bodies do not all come into an equal temperature at the 
same time. Caloric readily enters into some bodies, and freely 
combines with them, whereby their temperature becomes in- 
creased, and their properties sometimes changed. [See Part I., 
Construction, sec. Glass, p. 106.] 

From the foregoing remarks, it will easily be perceived that 
many of our operations, in the management of hot-houses, are 
not only theoretically wrong, but diametrically opposed to the 
laws of nature. Our methods of ventilation are wrong in prac- 
tice, because our notions are wrong in principle. We raise the 



PRINCIPLES OF VENTILATION. 261 

temperature of our houses by artificial means, and drive off the 
oxygen and aqueous vapor, without returning a supply. We 
admit the heat to escape through the laps and fissures of the 
glass, of which there is always enough in badly glassed houses 
to admit the escape of one fourth the heat radiated in the house. 
And, moreover, we allow one fourth more at least to be taken 
away by direct radiation from the glass, so that hardly one half 
of the heat generated is used for the purpose intended. And, 
lastly, we admit the external air into the house, to deprive the 
atmosphere of its moisture by condensation. Likewise, in sum- 
mer, we admit the external air, in Sirocco currents, to sweep 
through the house, carrying away the moisture daily by gal- 
lons; and which, if not returned in equal abundance, must 
speedily prove injurious to the plants. 



SECTION II. 

EFFECTS OF VENTILATION, & C . 

1. The ventilation of hot-houses, during winter, requires all 
the skill which the most experienced gardener has at command. 
It is a comparatively easy matter to openaod shut the sashes, or 
ventilators ; but to do so with benefit to the plants, at all times, 
requires an amount of skill which is seldom bestowed upon it. 
Admitting large quantities of cold air into a house, many de- 
grees below the internal atmosphere, cannot be otherwise than 
injurious to the plants growing therein. It has been calculated 
that a volume of air, equal to 400 cubic feet, will absorb up- 
wards of 36 gallons of water during its rise from 60 to 90° 
of temperature ; or, in other words, upwards of a gallon has 
been absorbed for every degree of temperature above 60°. This 
will, in some measure, show the propriety of keeping the walls 
and floors of a plant-house continually saturated with moisture, 
especially during the hot days of summer, as well as of pre- 
venting currents of air from sweeping through the house. We 
have succeeded, in this way, in keeping the atmosphere of a 
green-house 10 or 15° below the external temperature, even 
when the latter stood above 90° ; and almost every gardener, 
who has paid attention to these matters, has experienced the 
same results. It is a common error for gardeners to give large 
supplies of air, in sultry weather ; but, as it is a practical one, 
and one of long standing, it is excusable in those who have not 
studied its effects attentively. 

By far the larger number of gardeners attach great impor- 
tance to the ventilation of their houses abundantly, without per- 
haps sufficiently considering the nature of the plants they have 
to manage ; and, as has been justly enough said, by supposing 
that plants require to be treated like man himself. They con- 



EFFECTS OF VENTILATION. 263 

suit their own feelings, rather than the principles of vegetable 
growth. There can be no doubt, however, that the effect of 
excessive ventilation is more frequently injurious than advan- 
tageous ; and that many houses, and especially hot-houses, 
would be more skilfully managed, if the power of ventilation 
possessed by the gardener were much diminished. 

Animals require a continual renovation of the air that sur- 
rounds them, because they very speedily render it impure, by 
the carbonic acid given off, and the oxygen abstracted by ani- 
mal respiration. But the reverse is what happens to plants. 
They exhale oxygen during the day, and inhale the carbonic acid 
of the atmosphere, thus depriving the latter of that which 
would render it unfit for the sustenance of the higher orders 
of the animal kingdom ; and, considering the manner in which 
glass-houses of all kinds are constructed, the buoyancy of the 
air, in all heated houses, would enable it to escape in sufficient 
quantity to renew itself as quickly as it can be necessary for 
the maintenance of the healthy action of the organs of vegetable 
respiration. 

It is, therefore, improbable that the ventilation of houses, in 
which plants grow, is necessary to them, so far as respiration is 
concerned. Indeed, Mr. Ward has proved that many plants 
will grow better in confined air, than in that which is often 
changed. By placing various kinds of plants in cases, — not, 
indeed, air-tight, for that is impossible with the means applied 
to the construction of a glass-house, but so as to exclude as 
much as possible the admission of the external air, — supplying 
them with a due quantity of water, and exposing them fully to 
the light, he has shown the possibility of cultivating them with- 
out ventilation, with much more success than usually attends 
glass-house management. 

2. In forcing-houses, in particular, it will be evident from 
what is about to follow, that ventilation, under ordinary circum- 
stances, in the early spring, may be productive of injury rather 
than of benefit. Many gardeners now admit air very sparingly 
to their vineries during the time that their leaves are tender 
and the fruit unformed. Some excellent hot-houses have no 
23 



264 EFFECTS OF VENTILATION. 

provision at all for ventilation ; and we have the direct testimony 
of Mr. Knight, as to the advantage of the practice to many 
cases to which it has been commonly applied. 

" It may be objected," says Knight, " that plants do not 
thrive, and that the skins of grapes are thick, and that other 
fruits are without flavor, in crowded forcing-houses. But in 
these, it is probably light, rather than a more rapid change of air, 
that is wanting ; for in a forcing-house, which I have long devoted 
to experiments, I employ but very little fire heat, and never give 
air till the grapes are fully ripe, in the hottest and brightest 
weather, further than is just necessary to prevent the leaves 
from being destroyed by excess of heat. Yet this mode of 
treatment does not at all lessen the flavor of the fruit, nor ren- 
der the skins of the grapes thick. On the contrary, their skins 
are always moist, remarkably thin, and very similar to those 
grapes which have ripened in the open air." — [Hort. Trans.] 

We have experienced the same results, as those recorded by 
Mr. Knight, under similar treatment, and that too under a more 
powerful sun. We have pursued this method of giving a very 
limited supply of air, on an extensive scale, in some large 
graperies in Maryland, and under glass of the very worst possi- 
ble description. Yet, during one of the hottest summers which 
had been experienced for some years, these vines grew beyond 
anything we had ever seen, without any indication of injury by 
the sun's burning rays. The lower surfaces of the houses, how- 
ever, were kept moist, by frequent sprinkling with water during 
the day. Many large houses in England are never aired, 
except, perhaps, a few apertures at the top of the house, which 
are left open, night and day, during the summer. But in all 
cases within our knowledge, water is abundantly supplied to the 
atmosphere from the floors of the house. 

3. The philosophy of this method is easily perceived. The 
under surface of the glass is continually covered with a deposi- 
tion of the evaporated moisture, which intercepts the calorific 
rays, and prevents them from being concentrated on the leaves, 
from which cause the leaves are scorched and burned ; the 
atmosphere, at the same time, undergoing comparatively little 
change, or admixture with the external air. 



EFFECTS OF VENTILATION. 265 

While, however, the natural atmosphere of a hot-house can- 
not be supposed to require changing, in order to adapt it to the 
respiration of plants, it is to be borne in mind that the air of 
hot-houses, artificially heated, may be rendered impure by the 
means employed to produce heat, as will be seen from what has 
already been said on the principles of heating, in the preceding 
part of this work. Sulphuric acid gas, in variable quantities, 
escapes from brick flues, especially old and imperfectly con- 
structed ones, and various other unsuspected sources of impu- 
rity, an infinitely small quantity of which is sufficient to con- 
taminate the air, in respect to vegetable life. 

Drs. Turner and Christison found that y^^y of sulphurous 
acid gas destroyed leaves in forty-eight hours ; and similar effects 
were observed from hydro-chloric acid gas. Chlorine, ammo- 
nia, and other gases produce the same results, when their pres- 
ence is altogether undiscoverable by the olfactory organs. We 
also know that the destructive properties of air, poisoned by cor- 
rosive sublimate, by its being dissolved and evaporated in the 
atmosphere of a hot-house, is not appreciable to the senses. 
[See Chemical Combinations in the Atmosphere, sec. IV., for 
detailed information on this subject.] 

Ventilation is necessary, then, not to enable plants to exercise 
their respiratory functions, provided the atmospheric air is un- 
mixed with accidental impurities, but to carry off noxious vapors 
generated in the atmosphere of a glazed house, and to produce 
dryness, or cold, or both. Thus it is evident that air is given 
under many conditions, when it is not only unnecessary, but 
injurious. 

When air is admitted, to produce cold in the house, the 
external temperature must be lower than the atmosphere of the 
house. This effect, however, cannot always be produced by 
ventilation, as, in summer, if the houses be rightly managed, the 
reverse effect will be produced, as the external air is not only 
warmer but more drying in its nature than the air of the 
house ought to be ; therefore its admission can only prove inju- 
rious, rather than otherwise, as we shall afterwards show. On 
the other hand, if the external air be cold, its admission will 



2bb EFFECTS OF VENTILATION. 

produce dryness, which may also prove injurious under certain 
circumstances. 

4. When the external air is admitted into a glazed house, 
below the temperature of the air it contains, the heated moist 
air rushes out at the upper ventilators; or, if it cannot find 
egress, it is quickly condensed upon the cold surface, against 
which it is forced to ascend ; the latter rapidly abstracts from 
the plants, etc., a part of their moisture, and thus gives a shock 
to their constitution which cannot fail to be injurious. 

This abstraction of moisture is in proportion to the rapidity 
of motion in the air. But it is not merely dryness that is thus 
produced, or such a lowering of the temperature as the ther- 
mometer suspended in the house may indicate. The rapid evapo- 
ration that takes place, upon the admission of the air, produces a 
degree of cold upon the surface of the leaves, and of the pots in 
which they grow, as well as all other bodies around them, of 
which our instruments give no indication. To counteract these 
mischievous effects, many contrivances have been proposed, in 
order to insure the introduction of fresh air, warm and loaded 
with moisture ; such as compelling the fresh air to enter a house, 
after passing through pipes moderately heated, or over hot-water 
pipes surrounded by a damp atmosphere, which have been proved 
decidedly advantageous, and to which we will subsequently 
refer. 

If ventilation is merely employed for the purpose of purifying 
the air, i. e., for carrying off extraneous gases and vapors that 
may be generated by artificial heat, it should be introduced, by 
all means, with great caution ; and some expedient should be 
adopted for supplying it with moisture, as well as to warm it 
slightly on its passage inwards, more especially in cold, frosty, 
or windy weather. 

If it is only introduced for the purpose of lowering the tem- 
perature, as in mild and genial spring and summer weather, it 
may be admitted without any such precaution ; and the freedom 
of admission should be in proportion as the external and inter- 
nal temperatures approach each other in equality. 

In hot, sultry weather, air should be sparingly admitted, as 



EFFECTS OF VENTILATION. 267 

the same effects are produced by the excessive evaporation as 
by the currents of cold air, as will be afterwards shown. 

5. Ventilation is also required, in winter, in pits and frames 
where soft and succulent plants are grown, especially in pits and 
frames warmed with fermenting materials. In this case, much 
care and caution are necessary ; the object here being to carry off 
the superfluous moisture, in order that the succulent tissue of 
the plants may not absorb more aqueous matter than they can 
decompose and assimilate. Although these kinds of plants will 
bear a high degree of atmospherical moisture in summer, when 
the days are long and the sun bright, and when, consequently, 
all their digestive energies are in full activity, yet they are 
by no means able to endure the same amount in the dark, short 
days of winter, when their powers of decomposition, or diges- 
tion, are comparatively feeble. 

6. The thermometric changes are by no means satisfactory 
guides for regulating the admission of air in hot-houses, as the 
effect required by the indications of the thermometer may be 
produced without resorting to the admission of air. In hot- 
houses, we have full control over the state of the atmosphere, 
both as regards its moisture and temperature ; and the means 
of exercising this power ought to be known and familiar to 
every gardener. But there are many circumstances which 
ought to be duly considered in the exercise of this power, and 
some unsuspected results arise from the unlimited use and exer- 
cise of it ; and, as has been already said, by far the greater 
number of gardeners attach too much importance to the mere 
opening and shutting of sashes, windows, etc., without duly 
studying the rationale of the practice. We will show that the 
practical effects of ventilation are not only different from what 
many suppose, but are actually injurious. 

During winter we are in the habit of raising the temperature 
of our hot-houses, by artificial heat, to 45 or 50° ; then, for six 
or seven hours during the day, we open the lights and admit a 
large quantity of cold air. This is also a stumbling-block, on 
which a great many gardeners fall ; for it is not solely to the 
23* 



268 EFFECTS OF VENTILATION. 

temperature, but rather to the hygrometrical state of the atmos- 
phere, we ought to look. We ought to regulate the admission 
of air, not solely by the thermometer, but also by the hygrome- 
ter ; for, upon the latter condition, the health of the plants, and 
the perfection of their flowers and fruit, very much depend ; — 
and, consequently, it is a matter which ought to be studiously 
considered. Nothing is more injurious than the admission of 
currents of air when the external temperature is lower than the 
internal one; and more especially so to plants that have been 
for a considerable time subjected to a high temperature by arti- 
ficial heat. 

The causes which operate in rendering the atmosphere of 
hot-houses unnaturally arid may be said to be two-fold. The 
rirst is the condensation of moisture upon the glass, arising 
from the action of the external cold upon its upper surface. The 
second is the escape of heated air through the laps and crev- 
ices oi the glass, and otherwise. This heated air escaping, car- 
ries along with it a large quantity of contained moisture, the 
loss of air being supplied with cold, dry air, which finds access 
by the same means. The loss of heat and moisture sustained 
by these means is far more than would be supposed by those 
who have not calculated the amount. 

7. We have seen that the quantity of moisture a cubic foot 
of air will hold in invisible suspension depends on its tem- 
perature ; and as the temperature is increased, so is its capacity 
for moisture. Suppose, then, that this capacity is doubled 
between the temperature of 40 and 60° ; that is to sav, even- 
cubic foot of air that enters the house at 40°, and escapes at 60°, 
carries with it just double the quantity of moisture it brought in. 
Now, every one must be sensible that these circumstances, con- 
tinued for any length of time, must render the atmosphere of 
the house too arid for healthy vegetation ; and, consequently, if 
the deficiency of moisture so occasioned be not supplied by 
artificial evaporation, then the plants must part with their secre- 
tions to supply the atmospheric demand, and the soil and other 
materials in the house will also be drained of their moisture, to 
make up the deficiency. The greater the difference between 



EFFECTS OF VENTILATION. 2b9 

the internal and external temperature, the greater will be the 
demand for moisture. Thus, if the external air be at the freez- 
ing point, (32°,) and the air in the house heated to 50 degrees, 
then there is three times more moisture carried away by escap- 
ing air than is brought in by the returning quantity ; and, 
escaping at 90°, it carries away four times as much, and so on, 
in proportion to the difference of the two atmospheres ; the ex- 
ternal air, however, increasing in ratio as it decreases m tem- 
perature. 

According to these calculations, atmospheric air, entering a 
house at 32°, and escaping at 100°, carries away nearly six 
times as much moisture as it brings in. This, in a short time, 
would render the atmosphere of a house deleterious to either 
animal or vegetable life ; and in large and lofty houses this is 
practically the case. We have managed a lofty plant-bouse, 
where the plants on the side shelves were nearly frozen, while the 
thermometer, hung in the angle of the roof, about 45 feet high, 
stood at 100 degrees. Now this heated air, escaping at the top 
of the roof, as is generally the case as well as here, carried away 
more moisture than the small evaporating surface could supply; 
the effects were, consequently, ruinous to the plants. However 
imperfect the above calculations may be, they are within the 
bounds of truth, and are sufficiently accurate to show the im- 
portance of this subject to exotic horticulture ; and it will more 
effectually impress upon our minds the amount of care and con- 
sideration which the ventilating of hot-houses demands. If air 
must be admitted, for the purpose of regulating the internal 
temperature, ever}' precaution should be taken to prevent it 
from entering in strong currents, and it should be taken in from 
the warmest side of the house, and, if possible, over a warm 
surface, — as hot-water pipes, or whatever heating apparatus may 
be employed, — so that the internal atmosphere may be gradually 
reduced ; and, at the same time, the utmost precaution should 
be used to prevent the escape of heated air, at least as little as 
possible, by direct ascension ; this is easily accomplished by the 
improved methods of ventilation now adopted, some of which I 
shall hereafter endeavor to describe. Thus the cultivator is 
enabled to modify the two atmospheres, previous to their com- 



EFFECTS OF VENTILATION. 

bination, and by raising the humidity in the atmosphere of the 
house, to compensate for that carried away by the egress of 
heated air, the plants will breathe an atmosphere more con- 
ducive to their healthy development, and will be benefited by 
the change. 

8. Every gardener has observed the water on the under sur- 
face of the glass, in the morning, before the sun has risen, 
warmed the glass, and driven it off again, in the form of aqueous 
vapor. This affords us a good illustration of the immense quan- 
tity of moisture carried upwards by the heated air, and depos- 
ited upon the glass, by condensation. This moisture is, of 
course, taken away from the plants, and other bodies capable 
of giving it off, and is demanded by the air as it becomes warm, 
and capable of carrying a larger quantity tban when no fire was 
applied, — or rather, when the temperature of the house and 
the temperature of the external air were alike, for in such case 
no condensation on the glass would take place ; and, as I have 
remarked, the proportion of water deposited will be in exact 
ratio to the intensity of the external cold ; thus, the greater 
the difference, the greater the deposition ; for then the action 
of the external cold upon the upper surface of the glass being 
greater, and the two atmospheres being brought into more rapid 
proximity, the particles of heated air are cooled as quickly as 
they ascend to the under surface of the glass ; they then fall to 
supply the place of others, leaving the contained moisture upon 
the cooling surface, in the form of dew, — the same process 
being repeated through the whole night, or until an equality of 
temperature is established ; the quantity thus deposited amounts 
to immense volumes of water. 

9. Experiments have proved that each square foot of glass 
contained in the roof of a hot-house will cool down 1J cubic 
feet of heated air per minute as many degrees as the temper- 
ature of the internal exceeds that of the external atmosphere. 
Suppose, for instance, that the external air stands at 40°, 
and that of the house 60° ; then, for every square foot of 
glass contained in the house, one and one fourth cubic feet of 



EFFECTS OF VENTILATION. 271 

air will be cooled down the 20 degrees ; thus, 60 minus 40 gives 
the difference, which is 20. If the house contains 800 square 
feet of glass, presented to the action of the external atmosphere, 
1000 cubic feet of air will lose 20 degrees of heat ; consequent- 
ly, the moisture this air held in invisible solution, in virtue of 
its 20 degrees of temperature, will be condensed by the external 
cold, and deposited on the glass'; and it will also be found, that 
the greater the difference between the external and internal 
temperatures, the greater will be the amount of condensation. 
The quantity of moisture abstracted from plants, at high tem- 
peratures, is enormous. This fact is sufficiently demonstrated 
in a hot summer day, when the leaves of the trees are wilted, 
and the garden vegetables flag and droop their leaves. The 
earth gives out its moisture, and the atmosphere carries it away. 
The same thing takes place in hot-houses ; the moisture is ab- 
stracted by the heated air, and is carried off in the form of 
invisible vapor, till its upward progress is arrested by the glass, 
and the cold again reduces it to water. 

If we take, for example, the roof of a hot-house, comprising 
750 superficial feet of glass, and calculate that every square foot 
of that glass will cool down 1| cubic feet of heated air 36° 
per minute, and calculating the internal temperature at 65°, we 
shall find that 937 cubic feet of air will be cooled down 36 de- 
grees per minute. Now air, saturated at the temperature of 65 
degrees, contains about 6-59 grains of water per cubic foot, and 
at the temperature of 30 degrees, it is saturated with 2*25 
grains ; this gives 4*34 grains of water lost, in condensation on 
the glass, per minute ; or further, each square foot of glass con- 
denses \\ cubic feet, or about 5*42 grains of water, per minute ; 
and supposing the atmosphere of a house, such as we have de- 
scribed, to be constantly supplied with moisture, by evaporation, 
or otherwise, there would be abstracted from it about |- of a pint 
of water per minute, which is about 12 quarts per hour, or at 
the rate of nearly 72 gallons in 24 hours. This enormous 
amount of water, evaporated into the atmosphere of a hot-house, 
when reduced to calculation, and displayed in plain figures, 
seems to startle the imagination, and looks very like exaggera- 
tion; although it is much below the mark which, by a more 



272 EFFECTS OF VENTILATION. 

accurate calculation, it would certainly reach, yet the accuracy 
of these calculations will appear sufficiently obvious to any one 
who has paid studious attention to the subject. I say studious 
attention, because a person may be tolerably observant of atmos- 
pheric phenomena, and yet not form anything like an accurate 
idea of this extraordinary process going on in his presence, and 
the effect thereby produced on the vegetable system. When 
we enter a hot-house, on a cold, frosty morning, after a strong 
fire has been kept up during the night, we are very apt to regard 
the moisture condensed upon the lower surface of the s;lass 
as an evidence of a healthy atmosphere and luxuriant veg- 
etation ; and often have I heard it stoutly asserted, that it 
was merely the effect of an excess of moisture in the atmos- 
phere of the house. This may be partly true, but the conclusions 
which are drawn from the fact are founded on misconception, 
that the moisture thus deposited on the glass has already per- 
formed its purpose of benefit to the plants. 



SECTION III. 

METHODS OF VENTILATION, &C. 

1. If we admit the truth of the foregoing calculations, (and 
we cannot justly reject them, until they are disproved by calcu- 
lations more accurate, and observations more extended,) then 
we must acknowledge, also, that the old methods of ventilating 
hot-houses, which are still in common practice, are contrary to 
what we know to be right. Hence the question arises, How 
are these methods to be improved ? Now, I would remark, that 
the mere system on which a house may be ventilated is of com- 
paratively little importance, for no method of ventilation will be 
good, if the atmosphere be unskilfully managed. Various plans 
have been employed to modify the influence of draughts, or 
currents of air, many of which can hardly be termed improve- 
ments, since the general effect is the same as by the old method 
of opening the top and bottom sashes, which admits a current 
to rise up beneath the under surface of the glass, and, as it pro- 
ceeds towards the aperture made by letting down the upper 
sashes, it carries the ascending moisture along with it, without 
in the slightest degree mixing with, or purifying, the volume of 
atmosphere contained in the lower portions of the house. 

2. It has long been an object among gardeners to obtain a 
motion in the atmosphere of a hot-house ; and to secure this, 
even machinery has, in some instances, been employed, and, 
under certain conditions of the atmosphere, these machines may 
go on very well. But subject to those vicissitudes of climate, 
so prevalent in many parts of this continent, the consequent 
result of their adoption is, a complete derangement of all that 
equalizing regularity which they were intended to secure. It 
appears to us a matter of considerable difficulty to lay down a 
definite rule, or propose a particular system of ventilating a 
house, since almost every locality has some characteristics pecu- 



274 METHODS OF VENTILATION. 

liar to itself. It is true, the elements of the atmosphere may be 
nearly the same in one place as in another ; but they are influ- 
enced by various circumstances, in different localities, and hold 
soluble matters in suspension in very different proportions ; and 
in places much screened by trees, buildings, and similar objects 
of shelter and obstruction, air may be admitted with greater 
impunity than in situations exposed to wind from every quarter 
of the compass, — the latter condition, as a matter of course, re- 
quiring more care, not only in the adjustment of the apertures 
of admission, but also in the admission itself. The course of 
the current of air, by the common methods of ventilation, — that 
is, by opening the front, and letting down the top sashes, — is ex- 
ceedingly variable ; sometimes the actual motion created in the 
atmosphere is little more than a foot, or fourteen inches, below 
the surface of the glass. This motion can be easily determined 
by holding the flame of a candle in the current, when the flame 
will incline towards the aperture of egress ; lower it gradually 
down, till it assumes and maintains a perpendicular position, 
being no longer affected by the current, the volume of air being, 
in fact, stationary, except there be some aperture of ingress else- 
where. We have found this simple operation exceedingly useful 
in determining the currents of air in large houses, and, in most 
cases, it seldom fails in giving an accurate indication of their 
course. 

However desirable a motion may be in the atmosphere of a 
hot-house, — and I do not doubt but it is beneficial, — yet it is not 
necessary that we should run headlong either upon Scylla or 
Charybdis. There is a great difference between a motion in 
the atmosphere created by the warm particles ascending, and 
being replaced by the denser and colder air, and that created by 
a tornado sweeping through the house. The former motion is 
only perceptible to the eye of the attentive and experienced cul- 
tivator, and he can tell at a glance, by the quivering of the 
leaves, that they are fanned by a gentle zephyr. I am aware 
that some gardeners have a peculiar fancy for seeing their plants 
and vine-leaves bristling about by a good wind, and may be 
very successful, too, in their productions; but it cannot be as- 
serted that it is compatible with a high state of gardening skill, 



METHODS OF VENTILATION. 



275 



or with that perfection in horticulture at which it is our duty to 
aim ; inasmuch as the revelations of science are against it, as 
has already been shown, and practice has hitherto given no evi- 
dence to prove it beneficial to tender plants. 

3. In large and lofty structures, and especially in dome-shaped 
houses, the management of the atmosphere becomes a matter 
of much more importance than in small houses. During mild 
and temperate weather, things may go on very well, as at such 
times the external air may be allowed to circulate through the 
house with greater impunity ; but during the heat of summer, 
and the cold of winter, the atmosphere is much more difficult to 
equalize. With a frosty air externally, and the temperature at the 
surface of the earth down to zero, it is impossible to maintain a 
proper degree of temperature, in all parts of the house, without 
positive injury to those plants that may be growing, or have 
their branches extended into the upper regions of the house. In 
fact, without the precaution of covering, or some such expe- 
dient, mischief is absolutely unavoidable. What has already 
been said, upon the nature and properties of air, will sufficiently 
explain the cause ; and, although it has been repeatedly asserted 
by theorists, that one part of a house being heated by radiation, 
from a body radiating heat, the equalizing law of nature will 
heat all parts of the house to the same temperature, and as 
speedily, too, yet we must enter our decided protest against 
the practical correctness of such a statement ; at least, in our 
own practice, we have never found it so, under any circumstance, 
or by any system of heating. And hence, whatever the natural 
law of equality may be, the practical effects cannot be mistaken, 
or disputed, as far as regards hot-houses. We know that heated 
bodies tend to an equality of temperature ; but, as has been 
already observed, air, of all other bodies, possesses peculiar 
properties in this respect in regard to heat, and in nothing is this 
peculiarity more strikingly illustrated than in the case under 
consideration. 

4. With regard to the motion of the atmosphere in a hot- 
house, we know that the greater the difference between the tem- 
24 



276 METHODS OF VENTILATION. 

perature of the air entering the house and the atmosphere of 
the house itself, the greater will be the movement produced 
among the particles. The motion is in exact proportion to the 
difference of temperature ; and hence the necessity of admitting 
the external air, in small quantities, when the external ther- 
mometer is low. The slightest cause that disturbs the equilib- 
rium of the air produces a motion. It is more sensible than 
the most delicate balance. It is put in motion by the slightest 
inequalities of pressure, and by the smallest change of tempera- 
ture. It is speedily rarefied by heat, and thereby rendered 
specifically lighter than the neighboring portions, so that it 
descends, while colder, and consequently denser, flows in, to re- 
store the equilibrium. It will be easily seen, from the very 
nature of this law, that an equilibrium cannot be maintained in 
the artificial atmosphere of a hot-house, since the source of 
radiation must necessarily be confined to too small a surface to 
equalize the ascending heat; and, on the other hand, the con- 
densation by cold is too irregular throughout the heated vol- 
ume. This irregularity, produced by its unequal action on 
different parts of the house, must ever render it impossible to 
obtain an equality of temperature throughout an atmosphere 
heated by artificial means ; and the larger the house, the greater 
will be the difficulty of maintaining an equilibrium in its various 
parts. So much so is this the case, that, as has been already 
stated, the difference has been found to amount to 100°. 

" Gaseous bodies expand equally for an equal increase of 
temperature, as measured by the thermometer. Gay Lussac 
showed that 100 measures of atmospheric air, heated from the 
freezing to the boiling point, became 137.5 measures ; conse- 
quently, the increase for 1S0° Fahrenheit is ^f of its bulk. 
Dividing this quantity by ISO, we find that a given quantity of 
dry air expands ^-^ of the volume it occupied at 32°, for every 
decree of Fahrenheit. New experiments have been made by 
Rudberg, within a few years, giving ±^ T as the ratio of expan- 
sion for one degree of Fahrenheit ; and these results are con- 
firmed by Regnault. This last number may be adopted as the 
true increment. 

M If we wish to ascertain the volume which 100 cubic inches 



METHODS OF VENTILATION. 



277 



of a gas at 40° would occupy at 80°, we must remember that it 
does not expand ^- T of its bulk at 40° for each degree, but ¥ | T 
of its bulk at 32°. Now, 491 parts of air at 32° become 492 
at 33°, become 493 at 34°, and so on. Hence we can institute 
a proportion between the volume at 40° and that at 80°. * 

Vol. at 40°. Volume at SO 3 . Cubic inch. Cubic inch. 

491 + 8 : 491 + 48 : : 100 : 108 

>c j*LF 5. The annexed cuts represent 

an improved method of ventilating 
lean-to houses, and by which the 
Fig. 52. 



% 



-m 




c ©= 



Fig. 53. 



Fig. 51. 




* Wyman on Vent. 



278 METHODS OF VENTILATION. 

whole house may be aired in the space of one minute ; or as 
many houses as may be in the range. This is effected by a rod 
passing along the whole length of the house. A pulley is fixed 
immediately above each ventilator, and another placed opposite 
it upon the rod, as shown in Fig. 51. A piece of chain or cord 
is attached to the ventilator at one end ; and passing over the 
pulley, as shown at a, Fig. 52, is then fixed to the pulley placed 
opposite it upon the rod. A larger wheel, or pulley, is fixed at 
one end of the rod, (b,) to which is attached a chain, connected 
with a crank, situated within the reach of a person standing on 
the floor. This crank is fixed on the back wall, as seen at c, 
Fig. 52. 

From the foregoing cuts and description it will be perceived 
that, by giving the crank (d) a few turns, the whole of the ven- 
tilators will be opened. The crank is provided with a racket, so 
that they may be opened to any distance, from half an inch to 
the full height. 

The ventilators in the front wall may be opened and shut by 
the same method, and may be, for convenience, brought from the 
outside. Any length of house, or any number of houses, may 
be ventilated at once by this method, providing the apertures 
are in a straight line; their perpendicular distance from the 
horizontal shaft makes no difference in their facility of working. 
The pulley cords of the higher ones only require to be length- 
ened according to the distance, the diameter of the wheel on 
which the cord turns being equal all along the shaft. 

6. Figures 54 and 55 represent a method of ventilating 
span-roofed houses. It is employed in the houses at Frogmore, 

Fig. 54. 




METHODS OF VENTILATION. 279 

in England. Fig. 54 represents the end section of the house, 
with the ventilator in proportion to the other parts. Fig. 55 

Fig. 55. 




shows the sectional view of the ventilator, enlarged : a a are 
openings of admission, and are covered with lattice-work, to 
break the force of the current of ingress ; b, the movable shut- 
ter, which regulates the admission to and egress from the house. 
It is scarcely necessary to observe that these houses have been 
ventilated on the most approved principles; and it appears 
that several advantages are gained by this method. For in- 
stance, the current of heated air is arrested, in its progress 
outwards, by the depending glass at c c, and is, in some meas- 
ure, thrown downwards, preventing also the escape of its con- 
tained moisture. There is no doubt this method is very com- 
mendable for span-roofed houses ; and one of its advantages is, 
that the house can be aired, at any time, without the plants 
being saturated with rain. 

It is very possible that these compound systems of ventilation 
may excite a smile from some who have, all their lifetime, been 
accustomed to pull heavy sashes up and down for the purpose 
of giving air. But if we include, in one computation, the 
labor, the time, and the advantages of giving a range of houses 
three or four hundred feet long, air at the proper time, and all at 
the same moment, we will find a value in the system worthy of 
something more than the. mere smile of passive silence, which 
is too frequently all that is at first accorded to such improve- 
ments. 

In some establishments, instead of pulleys, toothed wheels are 
fixed to the shaft, which are made to work in a curved handle 
24* 



280 METHODS OF VENTILATION. 

attached to the front sash by means of a hinge. This curved 
rod is toothed on the lower side to answer the wheel, and is 
kept in its place by an iron staple, having an eye through which 
the sash-handle passes, as seen at a, Fig. 56. A crank and rachet- 



Fig. 56. 




wheel is provided, at one end of the shaft, by turning which the 
sashes are simultaneously opened and shut, to any distance. 
This method is simple and efficient. It has been extensively 
carried out in the unique assemblage of horticultural buildings 
at Frogmore ; and, as an improvement in the modes of ventilat- 
ing hot-houses, is considered, by competent judges, the most 
valuable contrivance that has been introduced during the last 
half century. By the turning of a small windlass, (which any 
child may do,) any quantity of air may be admitted, and in- 
creased or diminished at pleasure, throughout the whole range 
of buildings. 

The ventilation of forcing-houses, by this compound method 
of opening the whole sashes at once, is very liable to produce 
serious results, before the person in charge becomes fully 
acquainted with the management of it. This, like many other 
really valuable improvements in gardening, has been adopted, — 
bungled in the construction, — mismanaged afterwards, — then, 
lo ! it is condemned, with all the pomp and dignity of practical 
experience ! The present moment affords an ocular demonstra- 
tion of this too common fact. Some people suppose, if they 
can only get mechanical contrivances to accomplish certain ends, 






METHODS OF VENTILATION. 281 

that all is right. It is certainly desirable to employ mechan- 
ical contrivances, whenever they can, as in the present case, be 
applied advantageously. But mechanism can never make a 
gardener, inasmuch as the chief part of what constitutes a real 
gardener springs from mental, not physical, activity. It is a 
very easy matter to open and shut the ventilators of a hot- 
house ; but it requires something more than mere mechanical 
power to do so with certain benefit to the inhabitants within. 

This will be rendered clear by a common illustration. Let a 
dwelling-room be warmed to a temperature of 60° ; and suppose 
it to be tolerably well filled with individuals, by the animal heat 
and respiration of whom the room by and by becomes somewhat 
raised in temperature, and contaminated in its atmosphere. 
Then, all at once, let the windows be thrown open, and the con- 
sequence is not only disagreeable, but highly dangerous, as is 
manifest by the murmur which very soon pervades the assem- 
bled party. Now, the case is precisely similar in a hot-house, 
only with this difference, — the unfortunate plants cannot speak 
in audible sounds to tell the injuries that are perpetrated upon 
them ; yet they bear a language, imprinted on their leaves, no 
less truthful, nor less understood by the attentive observer. The 
above common occurrence is a plain illustration of what I have 
often seen, and have been forced to perform, in the ventilation 
of forcing-houses, and which is more likely to be exemplified by 
the compound methods w T hich I have described. Science may 
enable us to be more watchful of atmospheric phenomena, and 
may draw our attention to facts which mere practice might pass 
unnoticed. But this is a practical operation which science has 
not yet approached, and which, in all her discoveries, she never 
can approach, i. e., to tell us the precise quantum of air to 
admit at different times and under different temperatures. The 
method of mixtures does not come near it, and the combination 
of gases gives the gardener little scientific assistance. We must 
know the nature and properties of air at all times and tempera- 
tures ; but the quantities and proportions in which we are to 
admit it must be learned by experience and strict observation. 
We must watch its effects upon the plants, and admit it in 



282 METHODS OF VENTILATION. 

proportions which appear, by oft-repeated trials, to be most 
beneficial. 

7. We could describe several other systems of ventilation, 
by what we have called the compound method, which have a 
greater number of wheels and rachets, and other kinds of ma- 
chinery about them, but which possess no advantage over either 
of the methods we have described. One system, in particular, 
has received some countenance, which consists in opening by 
the aid of a spring instead of the toothed rod, as shown in Fig. 56. 
We have managed various houses ventilated by this method, but 
we must say that it worked badly, although much care had been 
taken to have the machinery properly fitted up ; for instance, 
where the springs are of unequal strength, — and by constant 
use they very soon become so, — you will find a very great irreg- 
ularity in the airing of the house, some of them requiring to be 
opened nearly full length, before the others will open a few 
inches. Again, if some of the sashes be stiff to open, those 
that are not so will open freely, while the ones that are hard to 
move will not open at all. This has frequently caused us much 
annoyance. It can never occur with the toothed wheel, as an 
equal force is exerted on each ventilator or sash, and every sash 
is opened to a regular distance. But if any of the sashes be 
stiff to open, then the whole power applied is directed upon 
them alone, until the whole move together. The only supposed 
advantage of the springs is, that they do the work silently, 
whereas a little noise is made by the rachet-wheels, — a matter, 
in most cases, of so trifling importance, as to be unworthy of 
consideration ; but, as drowning men catch at straws, so the most 
insignificant circumstance is eagerly seized, and magnified into 
momentous import, by would-be inventors, for the purpose of 
palming off their so-called invention upon the community, and 
sustaining its sinking reputation. The less machinery there is 
about a hot-house, the better ; and that system which does its 
work in the most efficient manner, with the smallest amount of 
labor, and is least likely to get out of order, is decidedly to be 
preferred. This is a commendation which cannot be justly 
given to some late inventions ; and, without wishing to throw 



METHODS OF VENTILATION. 283 

anything in the way of improving our present systems, or 
discouraging the application of new mechanical inventions to 
aid the practical operations of horticulture, we would say that 
some of these methods lately brought into notice may be 
justly compared to the putting of extra wheels to a carriage, 
increasing the rattling and complexity of the machine, but add- 
ing neither to the strength of the structure nor the rapidity of 
its course. 



SECTION IV. 

MANAGEMENT OF THE ATMOSPHERE 

1. Notwithstanding all the discussion which has taken 
place upon the abstract question of atmospheric motion, — and 
which, under certain temperatures, as we have already seen, 
cannot be disputed, — the true principles of \ T entilation still 
remain unsettled ; and the mechanical operation of admitting 
the air in larger or smaller quantities with facility does not, 
in the slightest degree, remove the general objections that have 
been urged against its effects on the internal atmosphere. In 
considering, therefore, the question, how far the admission of 
external air into forcing-houses is practicable and proper, it is 
necessary to ask, in the first place, For what purpose is the 
admission of external air resorted to under certain circum- 
stances ? and, secondly, How does it act upon the atmosphere 
when admitted ? 

The first of these questions is of comparatively easy solution : 
the latter requires more deep consideration, and more close 
investigation, before we can find a satisfactory reply. 

First. The necessity for ventilation arises from two prime 
causes, which are briefly these : to regulate and reduce the 
internal temperature ; and to allow the escape of impure air, or 
that portion from which some of the essential constituents have 
been abstracted by the plants, or in which the natural equiva- 
lents have been changed in their proportions, and consequently 
the health-imbuing balance destroyed, — an effect which may 
arise from various causes. The first of these points is a distinct 
consideration, forming an important branch in vegetable physi- 
ology : the others constitute a different branch of scientific 
research ; but in relation to our present subject, they both merge 
into one. 



MANAGEMENT OF THE ATMOSPHERE. 285 

The admission of cold air as the sole or principal agent in 
regulating the internal temperature of a hot-house during win- 
ter, seems to he perfectly unjustifiable. There are, indeed, 
times when it can hardly be avoided, during the application of 
artificial heat ; but these are exceptions, rather than the rule. 
Heat, when applied in early forcing, or to maintain the temper- 
ature of plant-houses, is artificial, and, therefore, so far unnatu- 
ral. And it appears still more unnatural to apply more than is 
necessary, for the purpose of admitting the external to cool 
down the internal atmosphere, without having secured any 
equivalent advantage, but rather lost, by the change. It is much 
more reasonable, as well as economical, to apply as much heat, 
and no more than is necessary, to raise the temperature to the 
minimum point, or, at least, as near this point as is possible. It 
may be supposed that it would be unsafe to keep the tempera- 
ture so close to the minimum point, lest the sudden external 
changes, to which we are subjected in this country in winter, 
might have an unfavorable effect upon the internal atmosphere ; 
and, under certain circumstances, this would be the case, — such 
as an imperfect heating apparatus, a badly glazed house, or a 
want of skill in the management of it. The necessity of main- 
taining the minimum rather than the maximum temperature 
has been already adverted to in the preceding chapter; and, 
instead of being the exception to a general rule, it is rapidly 
becoming the rule itself. We must consider that the object to 
be kept in view is to improve upon the means at present in use 
to obtain these results, and to obviate the risk and inconvenience 
which might otherwise ensue by their adoption. It will be 
observed, that it is not when the mild and genial weather of 
spring is experienced that these remarks have any forcible 
effect, but when the outward elements are unfavorable to the 
development of vegetable life. 

2. The atmosphere of a hot-house is very much influenced 
in winter by the glazing of the sashes, and the adjustment of its 
various parts. When the laps of the glass are open, there is a 
continual egress and ingress movement in the atmosphere adja- 
cent to the apertures, extending generally over the whole of its 



286 MANAGEMENT OF THE ATMOSPHERE. 

interior surface, but not always affecting seriously the internal 
volume, except in carrying off the rising particles of heated air, 
the greater portion of which is condensed by the cold air imme- 
diately as it escapes from the house. The consideration which 
refers to the escape of air in a deteriorated state, and the conse- 
quent necessity of admitting a fresh volume in its place, does 
not appear to offer any insurmountable difficulties to the belief 
that the admission of fresh air in the months of winter is very 
frequently carried to an injurious excess. Although plants, in 
the process of their growth, and in the discharge of their vital 
functions, abstract matters from the atmosphere around them, 
there is nothing, even in this, to render the admission of cold 
air in large volumes at all necessary. In considering the nature 
of the atmosphere in its relation to heat and cold, its elastic and 
all-pervading properties must not be lost sight of. Under any 
circumstances, a considerable effect will be produced by the 
external upon the internal atmosphere, by radiation alone ; and 
with the evidence before us of the successful growth of plants 
in situations so much closed up as in Wardian cases, we cannot 
do otherwise than believe that the interchange which takes 
place between the volumes by these causes is sufficient to secure 
the health and vigor of the plants, so far as the admission of 
air alone is concerned. If it be argued that deterioration will 
take place by means of evaporation from flues, or pipes, or any 
substances confined within the structure, or from the decomposi- 
tion of organic matter, the same fact is presented of an inter- 
change continually going on, and is sufficient to meet the case, 
so far as to show, that, on this ground, at least, the admission 
of external air in large volumes is not essential. Besides, with 
proper management, the gases that are generated by artificial 
heat, or by the decomposition of substances which should find a 
place in hot-houses, may be combined with others having an 
affinity for them, and thereby not only purifying the atmosphere 
by preventing an excess of particular agents, but also turning 
those agents to their legitimate purpose, and rendering them 
beneficial, rather than detrimental, to vegetable life. And, 
therefore, it can only be in cases where misapplication or gross 



MANAGEMENT OF THE ATMOSPHERE. 287 

mismanagement of some kind or other exists, that they can 
possibly be productive of injury, or even of inconvenience. 

These considerations, then, would seem to point out the fact, 
that the admission of air to any extent in forcing-houses in win- 
ter, or at a very early period of the season, cannot be said to be 
a matter of urgency, or necessity ; neither can it be grounded on 
the plea that many of our practical operations have for their 
foundation, viz., an expedient for a better, and probably more 
tedious, method of effecting the same results. Whatever impro- 
priety may appear in the above statement, it will be fully justi- 
fied by its truth, — if a dozen years' extensive practice in the 
management of hot-houses, both large and small, and in the 
working of forcing-houses throughout the winter, be worth any- 
thing, as well as the evidence of many of the best practical 
gardeners of the present day. Then we would say that the 
influx of large volumes of cold air is decidedly hurtful, even on 
other grounds than those advanced in a former part of this chap- 
ter. But, on the other hand, the opposite extreme must also be 
avoided. The process may not be altogether dispensed with, 
although every means ought to be taken to modify its immedi- 
ate effect upon the internal atmosphere. It does appear, never- 
theless, that the regulation of the internal temperature, i. e., the 
prevention of too powerful a degree of heat, when the source of 
that heat is the sun, is the only legitimate end to be effected by 
the practice. If there are any other real advantages, they are 
certain to follow. If air is admitted with this only in view, — 
and these advantages are not likely to be lost if air is not admit- 
ted when not required to effect this primary purpose, — periods 
of bright sunshine, then, may be regarded as the only instances 
in which a recourse to the practice is absolutely necessary. 

3. From a full investigation and consideration of this sub- 
ject, the conclusion at which we have arrived is, that, with a 
proper system and routine of management, as regards the 
application of atmospheric humidity and heat, the admission of 
large volumes of the external air into the interior of hot-houses 
is not by any means so essential as it is generally represented 
to be. Whatever other differences of opinion may exist with 
25 



288 MANAGEMENT OF THE ATMOSPHERE. 

respect to this practice, it cannot be denied that a risk is in- 
curred, and frequently an injury sustained, when cold air comes 
in contact with the active organs of tender plants. And, there- 
fore, if no other advantage be gained from the practice than the 
regulation of the temperature, then, except in cases where the 
heat is increased by the influence of the sun, and therefore 
uncontrollable, it would be a much wiser practice to apply a less 
amount of heat by artificial means, thus rendering it less neces- 
sary to allow the superabundant portion to escape, and conse- 
quently exposing the plants in a less degree to the risk to 
which we have alluded. 

4. Even in those cases in which it is really necessary to 
have recourse to the practice of admitting air, much injury will 
be sustained, though it may not be apparent at the time, by 
admitting it in a rash and improper manner. It should be con- 
trived so that the change to be effected may be brought about 
gradually, and the cold and heated volumes should be made to 
intermingle regularly together, and in a way that the internal 
volume will be equally affected by it. Thus, if it be desirable 
to admit a quantity of air equivalent to the reduction of 20° 
of temperature, then the first consideration ought to be the 
external temperature ; and the apertures of admission ought to 
be regulated according to the calculations given at pp. 164 and 
165, and in such a manner that the volume of air within the 
house will not be deteriorated thereby, nor deprived of those 
gases which are essential to vegetable existence. 

Secondly. How does the external air act upon the internal at- 
mosphere, when so admitted ? This portion of our subject is of 
more difficult solution, and requires a closer investigation, inas- 
much as it is influenced by various causes, such as the form of 
the structure, the method of admission, and the material of 
which the interior part of the house is composed ; for example, 
a house presenting a large surface of glass to the morning sun 
requires to be sooner ventilated than one whose largest glass 
surface has a western aspect, and a small quantity of air admit- 
ted early in the morning will keep the temperature down for a 



MANAGEMENT OF THE ATMOSPHERE. 



289 



longer period, than a larger portion, when the temperature of the 
house has increased ten or twelve degrees higher. Again, if 
the top sashes be opened first, which is generally done, then a 
much larger quantity of oxygen and aqueous vapor is carried 
off than at any other period of the day. We believe it is the 
practice of nineteen out of every twenty gardeners, to open the 
top sashes first; then, when the internal temperature rises, and 
more external air is necessary, the top sashes are opened still 
more ; and, last of all, the front sashes are opened to make a cir- 
culation; — a circulation, indeed! By the time the front sashes 
are opened, the two atmospheres are generally equalized. Now, 
I would ask, how is this circulation produced, and what are its 
effects ? Not by the superior density of either atmosphere, for 
both are the same, but by currents of wind, and draughts created 
by other causes ) and their effect is to carry off the moisture 
already too much reduced. The annexed figure represents a 

Fig. 57. 




method of admitting fresh air into a house w r hich obviates the 
evil here complained of. The air enters through the side-walls 
at a a, then passes along beneath the floor, and enters the house 
in the centre of the floor, at b. In this instance, no air is 
admitted at the top; hence, the air, passing through these drains, 
enters the house at a higher temperature than if admitted at 
the sides or top, and, becoming gradually warmed as it ascends 
through the aperture in the floor, rises until it is again cooled by 
action of the external air upon the glass, then falls towards both 
sides of the house, producing a motion somewhat similar to that 



290 MANAGEMENT OF THE ATMOSPHERE. 

shown by the arrows in the foregoing figure. By this method, 
air may be introduced into a house at any period of the day, or 
even at night; and while every advantage arising from the 
admission of external air is gained, the disadvantages are done 
away with, save and except by the crevices in the structure. 
In winter, if cold air must be introduced to regulate the internal 
temperature, some such method as that given above should be 
adopted; but at a more advanced season of the year, when a 
larger supply of air is necessary, provision must be made at the 
sides for that purpose. As to opening the top sashes first, and 
keeping them open till the last, it is a practice for which we are 
unable to obtain any satisfactory reason, and which we think 
will not bear a strict investigation. But, it may be asked, how 
is the temperature to be reduced, where, at an advanced period 
of spring, the sun shines more powerfully, and when the tem- 
perature of a hot-house will suddenly rise ten or fifteen degrees 
above the maximum point ? To answer this question, it is 
necessary to consider whether there be any other method of 
reducing the temperature than by expelling the heated air, by 
the opening of the top sashes. From what has already been 
said on this point, we think we are fully justified in disposing 
of this question in the affirmative. Of course, we do not allude 
to the ventilation of houses in summer, but in the months of 
autumn, winter, and spring. By introducing the external air in 
the manner described in the last figure, the atmosphere of a hot- 
house will be reduced to any given point as effectually, though 
not so rapidly, as if the heated air was expelled through the 
sashes at the top of the house. This is accounted for by the 
circumstance already explained, viz., that when two columns of 
air of unequal temperatures are mixed together, the tempera- 
ture of the whole is reduced, while its density is increased ; and 
hence, so long as the atmosphere continues to be heated by 
reflection or radiation, this cold air will continue to cool it down, 
so that nothing is lost, while all the essentials of vegetation 
contained in the atmosphere are retained. 

5. The materials of which the internal part of the house is 
composed have also a powerful influence on the ventilation of a 



MANAGEMENT OF THE ATMOSPHERE. 



291 



hot-house. Those houses whose internal bases are composed 
of open soil require less ventilation than those that are paved 
with stone or tiles ; and those that are paved with tiles, or other 
soft materials, require less than those formed of hard and highly- 
reflecting bodies ; dark-colored walls, also, are longer in raising 
the temperature of houses than walls painted white, and for this 
reason white is preferred to any other color, as well as for its 
clean and light appearance when contrasted with the dark-green 
foliage of the plants. But in houses that are perfectly transpa- 
rent on every side, and admit abundance of light, there is no 
reason to suppose a dark color would not be preferable to a light 
one, although we are well aware that some scruples may be 
raised against it. Its propriety, however, can only be ques- 
tioned as a matter of taste, not of utility ; for, with the advan- 
tages above alluded to, in a well-constructed green-house, so far 
as the management of its atmosphere is concerned, we would 
decidedly prefer a house having the interior painted with a dark 
color, although we are very sensible that the effect produced 
would be meagre and dull, and but little calculated to harmo- 
nize with the floral inhabitants of the house, or the feelings of 
those who admire them. 

Fig. 58. 




6. The above cut represents a house ventilated by the com- 
mon method, i. e., the upright sashes at the sides and the top 
sashes along the roof, which, in span-framed houses, are gener- 
ally about four feet long, or nearly square. In summer this 
method answers perfectly ; but in winter and early spring it is 
25* 



292 MANAGEMENT OF THE ATMOSPHERE. 

next to impossible to admit air without injury to the plants, and 
incurring the evils which have been already detailed. Such a 
house as this should, by all means, have these sashes made to 
open, when requisite, but should also be provided with an 
under-ground method of admitting air, when the weather is 
unfavorable for opening the top and side sashes ; and, in this 
country, this may be said to be the case for at least three 
months out of the twelve, during which time air can seldom be 
admitted in anything like a sufficient quantity, without a posi- 
tive, though perhaps at the time an imperceptible, injury to 
exotic plants. 

Various other methods have been adopted for imparting to 
the atmosphere of a hot-house all the freshness of the natural 
atmosphere, without a reduction of temperature corresponding 
to the amount of cold air admitted, and also to effect this with- 
out an increased consumption of fuel. The following simple 
method has been carried out with pretty favorable results : — 

7. Suppose a house already heated by the common flue. 
We would propose that a square chamber be built over the top 
of the furnace, and embracing the neck of the flue for two or 
three feet, if practicable. This chamber should have a drain, 
not straight, but of a serpentine or zig-zag form, laid through 
it, one of its ends communicating with the external air, and the 
other communicating with the interior of the house. Into this 
latter opening, a pipe, made of tin or zinc, should be fitted, of 
sufficient size for the admission of a good volume of air. Let 
this pipe be laid along the lateral surface of the flue nearest the 
front wall of the house, not in immediate contact with, but sup- 
ported by bricks, or some other means, at the distance of a few 
inches from the flue. Let that portion of the tube which passes 
along the front be perforated with holes, to facilitate the escape 
of the warm air, with which it will be filled, into the interior of 
the house. This done, let a number of small tubes, — say one 
for each light, or one for each alternate light, — be fixed through 
the front wall, or otherwise as may be convenient, one end 
communicating with the external atmosphere, and the other 
entering the perforated tube. These smaller tubes should be 



MANAGEMENT OF THE ATMOSPHERE. 

provided with valves to open and shut at pleasure, to any extent 
within the limits of their diameter, so that the apertures of 
ingress for the cold air may be regulated by the operator accord- 
ing to the state of the weather and the quantity of air required. 
The size of these tubes will depend upon the size and situation 
of the house. For instance, if the house contains a large inter- 
nal volume of atmosphere, the perforated tube would require to 
be at least eight inches in diameter, and the smaller about one 
half the size of the large ones. And now for its mode of action. 
It will be evident, that when fire is applied to the furnace, its 
cover (which forms the floor of the chamber) will become heated 
to a considerable degree. As soon as this takes place, the 
external valve of the drain, which communicates with the main 
tube, should be opened, when the external air wall immediately 
rush in ; and, by having to traverse the heated floor of the 
chamber aforesaid, will expand along the large tube connected with 
it, which, from being in contact with the heated air, will itself 
become warm. The radiation of heat, too, from the surface of 
the flue directly beneath it, will assist in maintaining the tem- 
perature of the tube ; so that, although a portion of the heated 
air will escape through the perforations in its upper surface, 
enough will be retained to effect the purpose intended, which is, 
to neutralize the effects of the cold air that will be admitted 
through the medium of the small lateral tubes, and which may 
be admitted in any quantity, to the full volume of their admis- 
sion. As the w r arm air rushes along the tube, it will mingle 
with that admitted by the small tubes ; and the cold air, enter- 
ing by the latter, will thus be modified, while a supply of fresh 
air will at the same time be circulated through the atmosphere 
of the house. 

S. The advocates of what has been called a " free system of 
ventilation" have, like many others, in practising and advocat- 
ing a favorite theory, in their excess of zeal, completely defeated 
the objects they sought to secure. The sole object of some of 
the advocates of the free system appears to be the prevention 
of a stagnant atmosphere. They admit an unlimited quantity 
of atmospheric air, at all seasons, to prevent this most terrible 



294 MANAGEMENT OF THE ATMOSPHERE. 

evil they call stagnation, and denounce the system of sealing up 
plants (as some of them have termed it) from all atmospheric 
influence but that exerted over them by their own tainted arti- 
ficial atmosphere. Now, a stagnant atmosphere, or any con- 
dition in the atmosphere of a hot-house approaching to stagna- 
tion, certainly cannot be otherwise than injurious to vegetation. 
This is a statement the truth of which will scarcely be called in 
question. But, although the prevention or removal of it has 
alw&.ys been the chief object of every scientific gardener, it can- 
not be said that every gardener, having this aim in view, has 
taken the right way to effect his purpose ; for, certainly, what 
is called " free " ventilation is very far from being the proper 
mode of obviating the evil ; and, in questioning the propriety 
of the system upon these grounds, it may be deemed necessary 
to enter into an explanation of the results attributed to this sys- 
tem of ventilation, which is said to be requisite in order to 
adapt an artificial air to the circumstances of the plants growing 
in it, and which is supposed by some to be in exact harmony 
with the laws of vegetable physiology, and with all that science 
has unfolded to us respecting the effects of the atmosphere upon 
vegetable life. 

The direct effects of ventilation, of any description, are two- 
fold, mechanical and chemical. The former embraces the influ- 
ence which motion possesses over the growth of plants ; and this 
influence has never yet been accurately defined or explained — 
whether it be injurious or beneficial, and in what particular 
degree it ceases to be so. The latter comprehends the effects of 
the various gases, and their influence upon the vital functions 
of vegetable beings. To illustrate the effects of the first of 
these agents, viz., motion, we may refer to the circumstance 
that is well known, that trees trained upon a wall, in ordi- 
nary circumstances, do not grow to such size as those standing 
in isolated places ; but their fibre is sooner matured, and also 
their fruit earlier, as well as larger and more saccharine. It has 
been asserted that wall trees do not arrive at so great an age as 
others standing in exposed situations, — an assertion as founda- 
tionless as it is absurd ; for it is a well-known fact, that wall trees 
have outlived others of the same kind, planted in similar soil, 



MANAGEMENT OF THE ATMOSPHERE. 295 

and at the same period with themselves. And yet this assertion 
has been made the basis of an argument in favor of free ven- 
tilation. [Experiments of Knight, in Philosophical Transac- 
tions.] 

Surely a system must be in a tottering condition when such far- 
fetched arguments are resorted to for its support. Nor is this a 
solitary instance of irrelevant arguments being brought to sup- 
port untenable systems, when in a sinking condition. When a 
plant is in a healthy and vigorous state, its sap is propelled 
through its various tissues by its own vital principle, aided by 
the combined influence of light, and heat, and moisture. And 
while its vital principle remains unimpaired, and these essentials 
of its existence unexhausted, its functions will continue in a 
state of activity, until some cause, known or unknown, occur to 
destroy them. 

Let us rehearse an argument which has been advanced to 
overthrow the above theory. " When a plant is young and suc- 
culent, through all its parts, then all goes on very well ; but 
when the plant becomes more matured, and its vessels less per- 
vious to the flow of sap, from its increased bulk, its approach to 
maturity, and probably its deadened susceptibility to the action of 
light and heat, it is evident that to prolong the existence of such 
a plant, a new impulse must be communicated to its sap, by a 
different species of agency from that which was necessary in the 
case of the young plant. This impulse is imparted by motion, 
and that motion is created by the winds and currents of the 
atmosphere." 

Such is the sum and substance of an argument which involves 
the solution of a most important problem in vegetable physiol- 
ogy ; and, to the merely superficial reader, it has something 
very plausible in its appearance, but, unfortunately, it will not 
stand to be strictly investigated, for then the very breezes that 
are brought to support it, would sweep it away. This is more 
especially true when the illustration is applied to the atmos- 
phere of hot-houses, upon which point enough has been already 
said in this chapter, regarding the mechanical effects of currents, 
to render further enlargement on this subject unnecessary. 



SECTION V. 

CHEMICAL COMBINATIONS OF THE ATMOSPHERE. 

1. With respect to the chemical effects of ventilation, upon 
an artificial atmosphere, there are two important things to be 
kept in view, in providing an artificial atmosphere for plants in 
a glazed structure ; namely, the nourishment they ought to 
receive from it, and how to maintain it in this nutrient state. 

It is needless, in this place, to enter upon the minute detail 
of the various substances which enter into the composition of 
plants, or of the various elements which combine to form the 
different bodies of which they are composed, — bodies, in them- 
selves so different in their qualities, yet so identical in their for- 
mulas, and consisting of the same elements, united together in 
the same proportions. This is one of those facts in chemical 
science which appear so very remarkable to those who have not 
directed their attention to chemistry, but are scarcely capable of 
being clearly comprehended and explained, even by those who 
have profoundly studied this branch of natural science. Starch 
and sugar — how different their properties ! — how unlike their 
uses! — how unequal their importance to the human race! 
Yet they consist of the same weights, of the same substances 
differently conjoined. The skilful architect can put together 
the same proportions of the same stone and cement; and 
the painter can combine the same colors, to produce a thou- 
sand varied impressions on the sense of sight. But in the hand 
of the Deity matter is infinitely more plastic. In his hands, 
and at his bidding, the same particles can unite in the same 
quantities, so as to produce the most dissimilar impressions, and 
on all our senses at once. 

A knowledge of the above close relations, in composition 
among a class of substances occurring so abundantly in plants, 
imparts a degree of simplicity to our ideas of this otherwise so 
very complicated subject. It does not appear so mysterious that 



CHEMICAL COMBINATIONS. 297 

we should have woody fibre, and starch, and gum, and sugar, 
occurring together in variable quantities, when we know that 
they all are made up of the same materials, in the same pro- 
portions ; or that one of these should occasionally disappear 
from a plant, to be replaced in whole or in part by another. 

A further question arises in our minds, in connection : Are 
these elements formed in an artificial atmosphere, such as that 
of a hot-house, from the same combinations of matter as in 
the natural atmosphere ? A reply, though probably not a satis- 
factory one, may be drawn from the following considerations : 

During the day plants assimilate carbonic acid, and evolve 
oxygen ; and during the night this system is reversed, although 
we have no accurate data from which to conclude that the rela- 
tive proportions of these gases are, at all times and under all 
circumstances, the same. From the latest experiments, we are 
induced to suppose that, in an artificial atmosphere, oxygen is 
the most important element to be attended to, in the regulation 
of its elements; and from the fact that its presence, to the 
amount of 21 per cent, in common atmospheric air, is essential 
to the existence of animals and plants, there can be little 
doubt that it is more frequently in deficiency, than in excess, 
in an artificial atmosphere, and that hot-house plants are more 
frequently injured by the want of a proper supply, than by an 
excess of it in the atmosphere, when we consider the quantity 
of this substance which nature has stored up for the use of 
plants and animals. Nearly one half of the solid rocks which 
compose the crust of our globe, — of every solid substance we 
see around us, — of the houses in which we live, and of the 
stones on which we tread, — of the soils which we daily culti- 
vate, — and much more than one half by weight of the bodies of 
all living animals and plants, — consist of this elementary body, 
oxygen, known to us only in the state of a gas. It may appear 
surprising that any one elementary substance should have been 
formed, by the Creator, in such abundance as to constitute nearly 
one half by weight of the entire crust of our globe. But this 
is not so surprising, when we consider that it is on the presence 
of this element that all animal and vegetable life depends ! Nor 
is it less wonderful that a substance, which we know only in a 



298 CHEMICAL COMBINATIONS 

state of thin air, should, by some extraordinary mechanism, by 
bound up and imprisoned, in such vast stores, in the solid moun- 
tains of the globe, — be destined to pervade and refresh all na- 
ture, in the form of water, and to beautify and adorn the earth 
in the solid parts of animals and plants. But all nature is full 
of similar wonders, and every step we advance in the study of 
the principles of our art, we cannot fail to perceive the united 
skill and bounty of the same great Contriver. 

2. It has been stated by some philosophers, that when the 
leaves of plants are in a state of rest, their respiration is reduced 
to its minimum point, and that it increases within certain limits, 
as motion is communicated to them by the action of a current 
of air. Now this may be perfectly correct, and very likely is 
so ; although, under natural conditions, the suspension of respi- 
ration has never been accurately ascertained. Various physiol- 
ogists have attempted to discover the minimum of respiratory 
suspension, under certain atmospheric conditions, but without 
any satisfactory results. But it does not require the discovery 
of this delicate point, to decide on the propriety or utility of 
atmospheric motion. That a certain motion in the atmosphere 
is beneficial, we know; but then, it becomes a question of degree. 
We know that the gentle zephyr is favorable to vegetation, and, 
even in a hot-house, we have some reason to suppose it is so, 
under certain circumstances, and to a certain extent. Now it is 
under the uncertain circumstances, and the uncertain extent to 
which this practice is carried, that we have any objections ; for 
such circumstances, and such indiscriminate abuse of the prac- 
tice, we know to exist ; and hence the chemical effects of venti- 
lation, in the majority of cases, instead of promoting respiration, 
rather tend to prevent it, by depriving the atmosphere of the 
principal element that nature has designed to carry on the work. 

The mechanical and chemical influences are intimately con- 
nected with each other, so that to secure the chemical ad- 
vantage of ventilation, I presume consists in maintaining the 
proper equivalents of the atmosphere, which nature has deter- 
mined as essential to the development of vegetation. If this 
view be correct, the grand and important practical question 



OF THE ATMOSPHERE OF HOT-HOUSES. 299 

suggests itself, whether, in the atmosphere of hot-houses gener- 
ally, these essentials to the growth of plants be suitably provided. 
By chemical research, we find that nitrogen forms only a 
small portion of plants, but it is never entirely absent from any 
part of them ; even when it is not found in any particular organ, 
it is found to be present in the fluids that pervade it. Many 
experiments have been instituted, with the view of ascertaining 
expressly, by what particular organs nitrogen entered into the 
plant, and in what form it enters. Indeed, this is a question 
which at present occupies much attention. It is well known 
that the leaves of plants absorb gaseous elements largely from 
the atmosphere, both free and in a combined state, and we might, 
therefore, expect that some of the nitrogen of the air would, by 
this channel, be admitted into their circulation. This view, 
however, is not confirmed by any of the experiments heretofore 
made, with the view of investigating the action and functions of 
the leaves. We are not at liberty to assume, therefore, that 
any of the nitrogen which plants contain, has in this way been 
derived directly from the atmosphere. It may be the case, but 
it is not yet proved. There is little doubt, however, that nitro- 
gen enters the roots of plants, in a state of solution ; but the 
quantity they thus absorb is uncertain ; it is supposed to be 
small, and must be variable. Therefore, by whatever organs it 
finds an entrance into plants, and in whatever quantity it may 
be present, the question still remains, that it is the ammonia of 
the atmosphere that chiefly furnishes nitrogen to plants. 

3. In a former part of this treatise, while treating on the 
subject of heating, by means of fermenting manure, we have 
alluded to the extraordinary effects of ammonia upon plants. It 
is unnecessary, at present, to recapitulate what has already been 
said on that interesting point. It has, we think, been clearly 
established, that the difference between a hot-bed of manure, and 
that heated by any other means, does not lie in the quality of 
the heat generated ; as we know full well that a hot-bed of 
manure, warmed beyond a certain point, will burn the roots 
of plants as quickly as one heated by any other method to the 
same temperature ; nor does it consist in any life-giving proper- 
26 



300 CHEMICAL COMBINATIONS 

ties, possessed exclusively by stable manure, for we know, also, 
that by placing living plants in a hot-bed, newly made, even if 
the heat of the bed be kept from injuring the roots, they will 
soon cease to exist as living beings, purely from an excess of 
those very gases which, in proper proportions, add so much to 
their natural luxuriance. Plants are more sensitive, and more 
easily affected, with regard to life and health, than many living 
animals. Many persons, who have paid little attention to veg- 
etable physiology, may be dubious of this fact, but it is, neverthe- 
less, true. The atmosphere of a hot-house may be impregnated 
with ammoniacal and other gases, beneficial to vegetable life, 
without being offensive to the ordinary visitor, or even detected 
by him in the atmosphere of the house. Besides, it is so quick- 
ly absorbed by the plants, that it has to be saturated almost to 
excess before much smell is sensibly felt. We have carried on 
the practice daily, of impregnating the atmosphere of a green- 
house with carbonate of ammonia, by dissolving it in water and 
sprinkling through the house, without the ammonia being de- 
tected, except by the acute olfactory organs of the experienced 
chemist, except, perhaps, when the atmosphere was impregnated 
to an excess, which, by way of experiment, was sometimes the 
case. 

4. This subject now resolves itself into the following consid- 
erations : — 

(1.) Which gases is it necessary to generate artificially, for 
the purpose of increasing the capacity of the atmosphere of a 
hot-house to sustain vegetable life in a state of vigor and health- 
fulness ? 

(2.) How are we to determine the precise proportions of each, 
so that we may keep as near as possible to that point of health- 
fulness, which lies midway between deficiency and excess ? 

In replying to the first question, it is not necessary to enter 
into an elaborate detail of the various volatile gases which 
arise from the combination of the prime elements of the organic 
world, in different proportions, and which are absorbed by plants. 
It may be sufficient for my present purpose, to notice that grand 
stimulus of vegetation already alluded to, viz., ammonia, which, 



OF THE ATMOSPHERE OF HOT-HOUSES. 301 

as we have already seen, plays such an important part in the 
progress of vegetable life. This gas, though composed of 
hydrogen and nitrogen, is very unlike these, or, indeed, any 
other gases with which the chemist is yet acquainted. It is 
possessed of a most powerful penetrating smell, which is familiar 
to almost every one as hartshorn and smelling-salts. In excess, 
it suffocates living animals, though it requires a very considera- 
ble preponderance in the atmospheric volume to destroy either 
animal or vegetable life. Illustrations of this fact we have fre- 
quently observed in fumigating a pit, or house, for the destruc- 
tion of aphides, and other insects ; but it destroys both, much 
more rapidly, when evolved at a high temperature, as we fre- 
quently find it in hot-beds of dung, when plants have been 
placed in them before the gas and heat had somewhat subsided, 
as well as in vineries, which we have seen filled with ammoni- 
acal gas, when the atmosphere was near 100 degrees, when the 
edges of the tender leaves appeared as if they had been nipped 
with frost, but the insects were not entirely destroyed. In 
fumigating frames and pits with this and other gases, we have 
seen some kinds of tender-leaved plants completely destroyed, 
while many of the insects, tenacious of life, were uninjured, 
which has fully satisfied me of the truth of the statement already 
made, i. e., that the generality of tender plants are more sensi- 
tive of noxious gases than living animals, although few may be 
inclined to believe it, and their disbelief is too often manifested 
in the treatment their plants receive. There can be little doubt 
that it is this gas, in a certain proportion of atmospheric air, 
that produces the luxuriance of plants, when combined with the 
mild heat of a dung-bed. Were we to ask a chemist, What are 
the manures which, in a fluid or gaseous state, can in these 
forms be presented to the atmosphere, and diffused among living 
plants, in a hot-house? — he would answer, "Ammonia, obtain 
it from whatever source you may, either in a simple or combined 
state ;" and as hitherto our chief supply of this substance, which 
we have had to deal with in the common operations of garden- 
ing, has been found in our hot-beds of stable manure, resulting 
from the decomposition of vegetable matter, principally the nitro- 
geneous substances contained in corn and other matter on which 



302 CHEMICAL COMBINATIONS 

the horses have been fed, with the compounds of salts and ani- 
mal matter, all of which contain within themselves a tendency 
to rapid putrefaction, and necessarily evolve a large amount of 
ammonia. This' is the principal source which gardeners have 
had to draw upon for a supply of this agent ; and, although 
exercising the most striking effects, it is rather remarkable that 
the cause of these effects should, until lately, remain a mystery 
to gardeners in general, and that the same elements, in a more 
concentrated state, should not, in other circumstances, be applied 
to produce the same results. 

The second question is, perhaps, of more difficult solution. 
Plants are living, organized, beings, and acted upon, atmospher- 
ically, chiefly by the glands that cover the surface of the leaves ; 
and abundant evidence exists, that they are as susceptible of 
either injury or benefit, through the medium of the atmosphere 
to which they are exposed, as animal life, and our ignorance of 
the effect of houses artificially heated, upon the delicate organ- 
ism of plants, is only accounted for from the fact, that com- 
paratively little attention has yet been paid to this branch of 
horticultural science by practical gardeners, and still less has it 
been applied to the culture of exotic plants. If, for instance, 
we take a plant from the open ground, where it is fully exposed 
to the pure air, plant it in a pot, and place it in a close living 
room, or in a hot-house, the effect will be rendered obvious by 
the altered appearance of the plant. Again, if we take a plant 
newly potted, and otherwise disturbed in the roots, and set it in 
an arid situation, and fully exposed to the air, the leaves will 
be withered and dried up in a few hours, and probably the death 
of the plant will be the issue. But if the plants are placed in 
a close, moist atmosphere, the results will be very different. 
Now these illustrations are common, and, in themselves, exceed- 
ingly simple, so much so, that we frequently observe them, and, 
if asked the cause, we give a kind of generalizing reply, by 
attributing it to the sun, or some such cause, which is well 
known to be the principal origin of heat, yet they serve to show 
how susceptible plants are of influences which, strictly speak- 
ing, are neither dependent upon heat nor cold, although these 
two latter elements are almost the only ones, which we are in 



OF THE ATMOSPHERE OF HOT-HOUSES. 303 

the habit of supplying to our plants by measure, and that, too, 
in the most unnatural proportions, while the ammoniacal and 
hygrometrical condition of the atmosphere is generally left to 
uncontrolled transmutations of chance. 

5. It may be asked, " What guide have we to ascertain the 
condition of the atmospheric gases ? " 

In the present state of our knowledge of gaseous bodies, their 
presence or preponderance in the atmosphere of hot-houses must 
be little else than a matter of conjecture. An experienced gar- 
dener, on entering his hot-house in the dark, can tell pretty 
accurately what degree of temperature the atmosphere of the 
house is standing at, by the sensation produced upon his face, 
or by the wave of his hand in the air. Now, in regard to the 
excess of volatile gases floating in the atmosphere, the organs of 
smell are much more delicate indicators than the sense of feeling. 
This is more especially the case when the house is close, and the 
temperature pretty high; for then the ammonia, being little more 
than half the weight of the common atmosphere, [more nearly 
three fifths, its specific gravity being 0.59, that of air being 1J 
hence, when liberated on the floor, or on the flue, pipes, tank, or 
other heating apparatus, it readily rises and mingles with the 
atmosphere ; and although it requires a considerable proportion 
of it in the atmosphere to be injurious, or even offensive to the 
senses, it is, nevertheless, easily detected by those acquainted 
with this gas, even when present in small quantities, and the 
experienced organs of the practical man have no difficulty in 
deciding whether or not it is present in excess. On entering a 
hot-house, when oxygen and aqueous vapor are deficient in the 
atmosphere, this fact is at once detected by the oppressive burnt 
smell which pervades the house. Saturate the atmosphere with 
water, oxygen is generated, and the smell ceases. The carbonic 
acid, which previously existed in excess, combines with the oxy- 
gen, and is transformed into carbonic acid gas, in which state it 
is assimilated by the plants. In the state of vapor, water exer- 
cises a wonderful influence over the atmosphere of a hot-house, 
and ministers most materially to the life and growth of plants. 
It is in the form of water, indeed, that nature introduces the 
26* 



304 CHEMICAL COMBINATIONS 

greater portion of the oxygen which performs so important a 
part in the numerous and diversified changes which are contin- 
ually taking place in the interior of plants, Few changes are 
really more wonderful, in chemical physiology, than the vast 
variety of transmutations which are constantly going on through 
the agency of the elements of water. 

It rarely, perhaps never, happens that we find the same 
unhealthy and disagreeable smell in the external atmosphere, 
which we frequently perceive in forcing-houses after a strong 
fire has been kept up during the night. Sometimes this condi- 
tion may occur in the confined streets of closely-built cities, and 
in the vicinity of chemical works, where the heavier gases rise 
into the air in a rarefied state, and, on cooling, fall again to the 
surface of the earth, producing sometimes injurious conse- 
quences. The combustion of fuel for the production of artificial 
heat produces also carbonic acid gas in great abundance. And 
to form this gas the oxygen is drawn from the plants to form 
the combination; and in this way the deficiency of oxygen, so 
much felt in forcing-houses, may partly be accounted for. Oxy- 
gen must exist in the atmosphere to the amount of 21 per cent. 
of its bulk to be capable of supporting animal and vegetable life 
in a state of vigorous development ; and when this proportion is 
reduced, the plants under its influence must suffer accordingly. 
The most convenient method of supplying the atmosphere with 
oxygen is by saturation with water, which latter element con- 
tains a very large amount of this gas, — every nine pounds of this 
liquid containing no less than eight pounds of oxygen. In the 
interior of plants, water undergoes continual decomposition and 
recomposition. In its fluid state it finds its way and exists in 
every vessel and in every tissue ; and so slight, it would appear, 
in such situations, is the hold which its component elements 
have upon each other, or so strong their tendency to combine 
with other substances, that they are ready to separate from each 
other at every impulse, yielding now oxygen to one, now hydro- 
gen to another, as the production of the several compounds 
which each organ is destined to elaborate respectively demands. 
Yet with the same readiness do they re-attach themselves, and 
cling together, when new metamorphoses require it. 

6. In the constitution of the natural atmosphere we are at 



OF THE ATMOSPHERE OF HOT-HOUSES. 305 

no loss to discover its beautiful adaptation to the wants and 
structural development of animal and vegetable life. The excit- 
ing effect of pure oxygen on the animal economy is diluted by 
the large admixture with nitrogen; the quantity of carbonic 
acid present is sufficient to supply food to the plant, while it is 
not so great as to prove injurious to the animal; and the watery 
vapor suffices to maintain the flexibility of the parts of both 
orders of beings, without being in such a proportion as to prove 
hurtful to either.^ 

The air, thus charged with these gases, by its subtilty diffuses 
itself everywhere. Into every pore of the soil it make its way. 
When there, it yields its oxygen, or its carbonic acid, to the 
dead vegetable matter existing therein, or to the living roots. 
When the soil is heated by the sun, the gases that are impris- 
oned therein expand and partially escape, and are as before 
replaced by other particles of air when the heat of the sun is 
withdrawn. 

By the action of these and other causes, a constant circulation 
is kept up, to a certain extent, between the atmosphere on the 
surface, which plays among the leaves and stems of plants, and 
the air which mingles with the soil and ministers to the roots; 

* The mutual influence of animal and vegetable life is well illustrated 
by the following experiment. Into a glass vessel, filled with water, put 
a sprig of a plant and a fish. Let the vessel be tightly corked, and 
placed in the sun. The plant, under the influence of solar light, will 
soon commence the process of liberating oxygen. This being absorbed 
by the water is respired by the fish, which, in its turn, gives out car- 
bonic acid to be decomposed by the plant. Kemove the vessel from the 
sun-light ; the plant will cease to give out oxygen, and the fish will 
soon languish, and revive when placed in the light. The moving power 
of this beautiful system is the solar light. The balance is thus pre- 
served ; and the atmosphere, even if of limited extent, cannot be sensibly 
changed through all time. 

It is not intended to intimate that it is in the removal of carbonic acid 
from the atmosphere that plants are most essential to animals, — the 
supply of organic matter ready for assimilation is of more immediate 
importance than this, — but to show that their influence is mutually 
conservative, preventing that change in the constituents of the atmos- 
phere which would eventually be fatal to organic life. — [Wyman on 
Ventilation.'] 



306 CHEMICAL COMBINATIONS 

and will also suffice to show the absolute necessity of maintain- 
ing an adequate supply of aqueous vapor in the atmosphere of 
our hot-houses, as well as the imperative necessity of studying 
and making ourselves acquainted with the nature and qualities 
of the atmospheric elements. Science has already done much, 
and is still doing more, for the art of horticulture. We have 
the thermometer, by which we can deal out heat and cold by 
the measure. We have the barometer, by which we can ascer- 
tain to a decimal the weight or density of the air. We have, 
also, the hygrometer, by which we can tell the precise amount 
of its contained moisture, — although this latter instrument is 
but little used in practical horticulture, — and we hope the time 
is not distant when it will find a place side by side with the 
thermometer in our hot-houses, to which it does not yield one 
iota of importance, of interest, or of utility. When shall we have 
an instrument, equally simple and efficient as these, with which 
we may ascertain the proportions of its gaseous elements, so 
that we can regulate the constituents of an atmospheric volume 
as easily as we can do its heat and moisture ? Such an instru- 
ment is much wanted by exotic horticulturists, and we trust 
something of the kind will be yet brought into use. Such an 
instrument could be applied to excellent purpose, and would be 
an incalculable boon conferred on gardening, — one almost un- 
equalled in importance at the present day, and would be of 
immense utility in all the higher and more difficult branches 
of exotic horticulture. 

7. There is, probably, no individual branch of natural science 
so useful in itself to the practical gardener as a knowledge of 
the various atmospheric phenomena which occur in hot-houses, 
as well as out of doors ; and without we study the one, we can 
have but little knowledge of the agencies which regulate the 
other. That a practical foreknowledge or intuitive perception 
of the ordinary changes of the atmosphere is an acquirement 
which may certainly be obtained, to a very considerable extent, 
without the aid of science, is beyond a doubt. We find that the 
untutored savage, taught only by his own observation, or instinct- 
ively, is regulated in his movements by an unerring perception 



OF THE ATMOSPHERE OF HOT-HOUSES. 307 

of the coming changes of his own peculiar climate, and many 
of the lower animals are also highly sensitive of changes ap- 
proaching, especially the feathered tribes. Every person is 
more or less familiar with these facts. We reason, therefore, 
from the lesser to the greater; and if, in the absence of compara- 
tive calculation, or the comparison of the results of one season 
with another, — if, in fact, we consider what are the attainments 
of instinctive knowledge alone, we are justified in believing 
that, from established principles, the result of learned inquiry 
and deep investigation, and the application of science extending 
over many successive years, many useful facts are already 
known and clearly explained for our practical guidance. Aided 
by these researches, man's ingenuity has already turned these 
elements to a useful account, and made them subserve his pur- 
pose, powerful though they be. But, in rendering these pow- 
erful and all-pervading elements subservient to our will, the 
object of that will must be undeviatingly directed to the imita- 
tion of nature. To exceed, or even reach, in every case, the 
perfection of the pattern, is impossible ; but the more closely it 
is kept in view, and the more nearly it is attained in our artifi- 
cial performances, the more perfect will that performance be, 
and the more exactly will our own ends be answered. Any 
departures from the principles suggested by the examples set 
before us in nature, through an over-hasty desire to arrive at 
the object by a nearer road, not only defeats the intended pur- 
pose, but also makes the ultimate attainment of that object 
much more troublesome and expensive. The subject of this 
treatise affords too many examples of this fact; and, though 
these examples may remain unnoticed by some, and uncared 
for by others, their baneful influence on the progressing art 
of horticulture is neither distant nor obscure. The various 
structures for cultivation are, indeed, much improved of late 
years ; so, also, are the methods of applying heat, air, vapor, 
and water. All are so easy, and so much improved, that we 
sometimes hear practical men observe, that this or that principle 
or system cannot be beaten or improved ; yet the very best con- 
structed apparatus, and the most perfect methods of applying 
heat, vapor, air, and light, are capable of astonishing improve- 



308 COMBINATIONS OF THE ATMOSPHERE. 

merits. And no doubt the next twenty years will bring many 
a hidden treasure to light, and, in that time, even oar most 
approved systems of applying heat, etc., will be altogether 
economized and reformed. 



SECTION VI. 

PROTECTION OF PLANT-HOUSES DURING COLD 
NIGHTS. 

1. Before concluding this brief treatise on horticultural 
buildings, we will just cursorily advert to one more topic con- 
nected therewith, which we are inclined to think is of far more 
importance than is generally credited, at least, it certainly is so, 
if we are to judge from the degree of its practical application, 
viz., the protection of plant-houses, and, more especially, forcing- 
houses, during cold nights, both with a view to the economizing 
of fuel, and the equalization of heat. If duly considered, the 
advantages of such covering are obvious. The low degree of 
night temperature, which the best cultivators of the present day 
agree in regarding as being most favorable to the healthfulness 
and general welfare of their plants, would depend upon the com- 
bustion of fuel, so much less, in proportion, as the escape of 
the internal heat, by radiation and otherwise, was prevented by 
means of a covering exterior to the conducting surface of the 
glass. 

The manifest advantage of such a protecting body does not 
wholly consist in the economizing of fuel. In such a variable 
climate as we have in the New England States, with the exter- 
nal atmosphere acting on the glass at a temperature of 25 or 30 
degrees below the freezing point, it is, then, almost under any 
system of heating, unavoidably necessary to apply an excess of 
artificial heat, to ensure the safety of the plants against injuri- 
ous depressions of temperature. Now, if a covering of non- 
conducting materials be employed to intercept the action of the 
changing atmosphere upon the surface of the glass, the plants 
will be as safe at a much lower internal temperature, as if no 
such protection were afforded them, with a high temperature. 
The plants, therefore, will, under these circumstances, be in a 



310 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 



condition more conducive to their health, than if their safety from 
excess of cold had involved their submission to a higher degree 
of artificial heat during the night. 

Night coverings, moreover, seem to afford facilities for night 
ventilation, — a time when ventilation, of all others, appears to be 
most necessary ; for then, deleterious gases are generated in 
the greatest abundance, and the agitation and circulation of 
the atmosphere is most required. We have seen that motion 
and interchange of atmospheric particles are, to a certain extent, 
beneficial to the health of plants ; and as their functions are in a 
state of activity during the night, motion and circulation are as 
necessary during that time as at midday. If a close confined 
atmosphere be injurious to plants in the daytime, it must be 
more so during the night, especially when artificial heat is in 
process of generation. This fact is now beginning to be recog- 
nized by the sounds, which are echoing in our ears — though as 
yet but faintly, — the injunction, to keep a little air on all night ; 
and which is responded to by the practice of the best cultivators 
of the present day. 

Under ordinary circumstances, where artificial heat is neces- 
sary, there is some risk in following these recommendations. 
A chilly blast, which cannot be refused admission when the bar- 
rier to ingress is removed, would deal death and desolation 
around ; and if this would be liable to happen in the daytime, 
when attendants are at hand, the risk would be still greater at 
night, when none were present to guard against it; and, under 
the most favorable circumstances, night ventilation, if carried to 
any extent, would involve a great loss of heat. It becomes, 
therefore, a question, if the motion and circulation of the inter- 
nal atmosphere during the night could not be so far facilitated 
by other means, as to secure the chief advantage of an actual 
interchange of air, without the internal heat being carried off by 
the cause that produced it ? 

Whatever prevents the radiation of heat from the interior to 
the exterior atmosphere through the conducting agency of glass, 
decreases in the same ratio the amount of required heat, and 
hence, saves the plants from being subjected to unnecessary 
excitement. The principle upon which a covering acts efn- 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 311 

ciently, is that of enclosing a complete stratum of air between 
it and the glass, this body of air being entirely shut off from the 
surrounding outer atmosphere, as far as may be practicable to 
do so ; and as air is a bad conductor of heat, the warmth of the 
interior is prevented from passing to the exterior atmosphere, by 
means of direct radiation from the glass ; or, in other words, the 
exterior atmosphere, being prevented from coming in contact 
with the glass, cannot absorb from the interior any sensible por- 
tion of its heat. To secure this advantage, it will be evident 
that the covering must be kept some distance from the glass, 
and should be on every side where the structure is formed of 
glass ; the coverings, in fact, should form a complete case to all 
the glazed portion of the structure.* 

So far, so good. As a matter of protection, and nothing else, 
this is all very well. The advantages of such a covering will 
be obvious to every one ; and, as a matter of protection alone, it 
deserves every word that can be said in its favor. Whether it 



# In the different experiments, it appears that the cooling effect of 
wind at different velocities on a thin glass surface, is very nearly as the 
square root of the velocity. In these experiments, the velocity of the 
air was measured by the revolutions of the vanes of a fan. The tem- 
perature of the air was 68°, the time required to cool the thermometer 
20° was noted for every different velocity, and the maximum tempera- 
ture of the thermometer in each experiment was 120°. In still air, it 
required 5' 45" to cool the thermometer this extent, and Table VIII. in 
the Appendix shows the time of cooling by air in motion. 

In consequence of the large quantity of glass used in the construction 
of horticultural buildings, the cooling effect of wind is of considerable 
importance. We find, however, that, with an increased velocity, the 
cooling effect is considerably less in proportion, on glass, than on metal, 
and it will be very much less on window-glass than even what is stated 
in the table. As glass is an extremely bad conductor of heat, the 
increased thickness which window-glass possesses over that which 
forms the bulb of a thermometer, will make a material difference in 
the quantity of heat lost by the abduction of the air, there will be, as in 
this case, a greater difference between the temperature of the external 
and the internal surface. The cooling effect of wind, therefore, is not 
near so considerable as is generally supposed ; and the effect of wind in 
hot-houses is very much increased by open laps and accidental fissures 
in the glazing of the sashes. 
27 



312 PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 

can practicably be made the means of admitting the external air 
into the house at an increased temperature, and thereby creat- 
ing a motion in the internal atmosphere, is a question which, as 
yet, we are unable to prove from experience, although we mean 
to take an early opportunity of testing the plan which we are 
about to describe. 

2. The best material which we have seen used for this pur- 
pose is canvas, or any other kind of strong coarse cloth, painted 
with two or three coats of pitch, wax, and oil boiled together, and 
applied in a warm state to the cloth ; this makes an efficient 
and durable covering. Asphalte felt is also used extensively 
in England and Germany for this purpose. This latter mate- 
rial is fixed on light wooden frames, about the size of a sash, or 
larger, as may be found convenient ; and for covering frames 
and pits it answers admirably, as it is quite impervious to wet, 
and if taken care of, will last for some years. But for covering 
the roofs of large houses, we would decidedly prefer the cloth, 
which can be more easily drawn off and put on, and, if well 
painted, will be as impervious to air and wet, as wooden shut- 
ters, or asphalte frames, and will be cheaper than either. 

Suppose, then, that a glazed cloth, of the requisite dimensions, 
is prepared. We would provide means for securing it against 
wind, by loops, etc., and fix on parallel strips of wood over each 
rafter, about nine inches from the glass. The cloth should be 
made to fit quite close at the top, and to reach the ground on 
all sides of the house, which, formed of conducting materials, or 
side-pieces, must be made to fit closely over the over-lapping 
edge of the upper one, and the lower edge secured against the 
admission of air. The house is now in a case, impervious both 
to air and water, and enclosing a stratum of air, which gradu- 
ally becomes warmer than the external atmosphere, and effectu- 
ally prevents the latter from abstracting the heat from the inte- 
rior of the house. Then let there be square holes made along 
the cloth, near the bottom, say one for each alternate light, each 
aperture made about ten inches square, and provided with a 
shutter of the same material, to close it when necessary. All 
these apertures, or any number of them, may be opened, accord- 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 313 

ing to the wind, or other circumstances likely to affect the inter- 
nal atmosphere. Then small apertures may be left open in 
different parts of the house, during the night, whereby an inter- 
change of the atmospheric volume would take place, without 
exposing the plants to immediate contact with the cold air. By 
this plan, we conceive that direct benefit would accrue to the 
plants, because the air between the covering and the glass, 
although not cold, would nevertheless be of greater density than 
that of the house, and would consequently find its way into the 
interior, by the ventilators left open for that purpose. This 
would also enable us to maintain a much lower night tempera- 
ture than could possibly be otherwise done, with regard to the 
safety of the plants, which the fear of sudden changes during the 
night, and consequent injury from frost, prevent from being 
realized in this changeable climate. 

It is truly remarkable how very slight a covering is required 
to exclude a pretty severe frost. " I have often," observes Dr. 
Wells, " in the pride of half-knowledge, smiled at the means fre- 
quently employed by gardeners to protect tender plants from 
cold, as it appeared to me impossible that a thin mat, or any 
such thin substance, could prevent them from attaining the tem- 
perature of the surrounding atmosphere, by which alone, I thought 
them liable to be injured. But when I had learned that bodies 
on the surface of the earth, become, during a still and serene 
night, colder than the atmosphere, by radiating their heat to the 
heavens, I perceived immediately a just reason for the practice 
which I had before deemed useless. Being desirous, however, 
of acquiring some precise information on this subject, I fixed 
perpendicularly in the earth of a grass plot four small sticks, and 
over their upper extremities, — which were six inches above the 
grass, and formed the corners of a square, the sides of which 
were two feet long, — fixed a thin cambric handkerchief, so as 
to cover the included space. In this disposition of things, there- 
fore, nothing existed to prevent the free passage of air from the 
surrounding grass to that which was sheltered under the hand- 
kerchief, except the four small upright sticks supporting it, and 
there was no substance to radiate heat downwards to the grass 
beneath but the cambric handkerchief. The temperature of the 



314 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 



grass, which was thus shielded from the sky, was, upon many- 
nights afterwards, examined by me, and was always found 
higher than the neighboring grass which was uncovered, if this 
was colder than the air. When the difference in temperature 
between the air several feet above the ground and the unshel- 
tered grass did not exceed 5°, the sheltered grass was about as 
warm as the air. If that difference, however, exceeded 5°, the 
air was found to be somewhat warmer than the sheltered grass. 
Thus, upon one night, when fully exposed grass was 11° colder 
than the air, the latter was 3° warmer than the sheltered grass, 
And the same difference existed on another night, when the air 
was 14° warmer than the exposed grass. One reason for this 
difference, no doubt, was, that the air which passed from the 
exposed grass, by which it had been very much cooled, had 
passed through that under the handkerchief, and deprived the 
latter of part of its heat. Another reason might be given, — 
that the handkerchief, from being made colder than the atmos- 
phere, by the radiation of its upper surface to the heavens, would 
remit somewhat less to the grass beneath, than what it received 
from that substance. But still, as the sheltered grass, notwith- 
standing these drawbacks, was, upon one night, as may be seen 
from the preceding account, S°, and upon another, 11°, warmer 
than grass freely exposed to the sky, a sufficient reason was 
now obtained for the utility of a very slight covering, to protect 
plants from the influence of frost or external cold."^ 

* As the elevation of temperature, induced by the heat of summer, is 
essential to the full exertion of the energies of the vital principle, so the 
depression of temperature, consequent upon intense cold nights, has been 
thought to suspend the exertion of the vital energies altogether. But this 
opinion is evidently founded on a mistake, as is proved by the example 
of such plants as protrude their leaves and flowers in the winter season 
only, as well as by the dissection of the yet unfolded bud, at different 
periods of the winter, which proves regular and progressive develop- 
ment ; even in the case of such plants as protrude their leaves and 
flowers in the spring and summer, and in which, as we have said, there 
is a gradual, regular, and incipient development of parts, from the time 
of the bud's first appearance, till its ultimate opening in the spring. The 
sap, it is true, flows much less freely, but it is not wholly stopped. Du 
Hamel planted some young trees in the autumn, cutting off all the 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 315 

We have instituted numerous experiments with the view of 
ascertaining the capacity of various substances for the protection 
of plants and horticultural structures, by which we find that 
bodies of soft and open texture, — as woollen netting, thin cloth, 
&c, — will, on dry, clear nights, afford an amount of protection 
equal to 7° of frost. But if the covering should become wet 
before the frost sets in, it will afford very little protection to the 
plants beneath it. 

Coarse cloth, which had been coated with paint, kept out 10° 
of frost, and several kinds of plants, which, at the freezing point, 
would suffer injury, were kept alive during the whole winter, 
with the thermometer occasionally indicating 22° of frost. These 
plants were frequently frozen, but the covering was never removed 
during several months, although the air circulated freely under- 
neath the glass. 

In protecting plants, or glazed structures of any description, it 
is essential to observe that the covering should always be placed 
so that a stratum of air may always be confined between the 
covering and the objects to be protected ; this is an important 
part of he matter, as, if the covering be laid immediately on the 
glass of a frame, or green-house, which it is wished to protect, 
the cold will be conducted by the covering to the glass, which 
in turn will cool the air beneath it. The covering should never 
touch the object to be sheltered, though, from what we see around 
us, this point appears to be very little attended to. 

A covering of thin cloth, or woollen netting, when suspended 
in a vertical position over trees, &c, will afford better protection 
than the same substance laid horizontally over the surface. In 
this manner, wall trees are protected in the British Isles from 
spring frosts, and we have frequently seen the blossoms of peach, 
apricot, and pear trees completely uninjured under woollen or 
hair netting, when the hardiest trees of the woods were nipt 
with frost, and the tender vegetables of the garden were entirely 

smaller fibers of the roots, with a view to watch the progress of the for- 
mation of new ones. At the end of a fortnight he had the plants all 
taken up and examined, with all possible care, to prevent injuring them, 
and found that, when they did not actually freeze, new roots were always 

uniformly developed. 

27^ 



316 PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 

destroyed. Peaches and other fruit trees might frequently be 
protected in this way, and the crop, at least, partly saved, instead 
of being, in one single night, blasted for the season. 

Common bass mats afford the best and cheapest protection for 
frames and small pits; but they have the fault of absorbing 
moisture very readily in wet weather, and then become very bad 
protection. They should never be laid on the glass in a wet 
state, as they are sure to do more injury than good. We have 
found it an excellent method, in covering frames and small 
houses with mats, to have a thin water-proof covering to lay 
over the mats, which not only prevents the escape of the con- 
fined air, but also keeps the mats always dry, and thus, one of 
the very best protectors is obtained. 

Large structures are more difficult to cover than pits, and the 
difficulty which thus presents itself has, in general, prevented 
every attempt to overcome it. We have seen various plans put 
in operation, besides that which we have already described ; all 
more or less effectual. The difficulty of getting common rollers 
to work in frosty weather has made them all but useless, in the 
protection of hot-houses by rolling blinds, or screens of oil-cloth. 
Nevertheless, this plan is not only an effectual one, but one 
which is cheap and easily adopted. And the cloth can be drawn 
off, in the mornings, and spread out to dry on the snow, or hung 
on a fence, during the day. When the time comes for covering 
at night, it might be so arranged as to be drawn up by cords 
passing through a pulley at each end of the house. We have 
succeeded in arrangements of this kind ; and the saving of fuel 
in a severe winter, with the certainty of the plants being safe 
from injury, either from frost or from fire, is ample compensation 
for the trouble which it costs. 

Whatever kind of object it is wished to protect, whether a 
house or a plant, the protector should always be at least one 
foot from it. A considerable difference of temperature is always 
observed, on still and serene nights, between bodies sheltered 
from the sky by substances touching them, and similar bodies 
which were sheltered by a substance a little above them. " I 
found, for example," says Dr. Wells, " upon one night, that the 
warmth of grass sheltered by a cambric handkerchief, raised a 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 317 

few inches in the air, was 3° greater than a neighboring piece 
of grass, which was sheltered by a similar handkerchief, which 
was actually in contact with it. On another night the difference 
between the temperatures of the two portions of grass, sheltered 
in the same manner as the two above mentioned, from the influ- 
ence of the sky, was 4°. Possibly," says he, " experience has 
long ago taught gardeners the superior advantages of defending 
tender plants from the cold of clear and calm nights, by means 
of substances not directly touching them, though I do not recol- 
lect ever having seen any contrivance for keeping mats, and such 
like bodies, at a distance from the plants which they were meant 
to protect." We know this to be a fact ; for gardeners seldom 
take any thought whether the plant is protected or not, provid- 
ing it be covered, with mats or something else, from the external 
atmosphere. 

Straw, and corn stalks, afford good protection to trees and half 
hardy shrubs, when properly arranged, so that the covering may 
be water-tight. The air that lodges among the straw, and in 
the interstices of the stalks, keeps the plant within, always at a 
regular temperature, and prevents sudden freezing and thawing, 
which prove the destruction of tender plants. 

Bodies, however, capable of absorbing heat during the day, 
and parting with it at night, when the temperature of the atmos- 
phere falls, are also useful as a means of protecting plants, &c. 
Among such bodies may be classed the walls of houses, which 
may be regarded useful in two ways ; namely, by the mechani- 
cal shelter they afford against cold winds, and by giving out 
the warmth, during the night, which they had absorbed during 
the day. It appears, however, that on clear and calm nights, 
those, on which plants frequently receive much injury from cold, 
walls must be beneficial in another way; namely, by preventing, 
in part, the loss of heat, which the plants would sustain from 
radiation, if they were fully exposed to the sky. The following 
experiment was made by Dr. Wells, for the purpose of deter- 
mining the justness of this opinion. A cambric handkerchief 
having been placed, by means of two upright sticks, perpendicu- 
larly to a grass plot, and at right angles to the course of the air, 
a thermometer was laid upon the grass close to the lower edge 



318 PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 

of the handkerchief on its windward side. The thermometer 
thus situated was, for several nights, compared with another 
lying on the same grass plat, but on a part of it fully exposed 
to the sky. On two of these nights, the air being clear and 
calm, the grass close to the handkerchief was found to be four 
degrees warmer than the fully exposed grass ; on a third night 
the difference was six degrees. An analogous fact is men- 
tioned by Gersten, who says that a horizontal surface is more 
abundantly dewed than one which is perpendicular to the 
ground. 

Snow forms an excellent covering, and seems to be a provis- 
ion of nature for the protection of many tender roots and plants 
which would otherwise perish. Its usefulness as a plant-pro- 
tector may be disputed, from the fact of their tops being exposed 
to the influence of the atmosphere, while their roots and lower 
parts only are protected. In reply to this, however, we may 
observe, that it prevents the occurrence of the cold, which bodies 
on the earth acquire in addition to that of the atmosphere, by 
the radiation of their heat to the heavens, in still and clear 
nights. The cause, indeed, of this additional cold, does not 
constantly operate, but its presence during only a few hours, 
might effectually destroy plants which now pass unhurt through 
the winter. Again, as things are, while low-growing vegetable 
productions are prevented, by the covering of snow, from becom- 
ing colder than the atmosphere, in consequence of their own 
radiation, the parts of trees and tall shrubs which rise above the 
snow are little affected by cold from this cause ; for their outer- 
most twigs, now that they are destitute of leaves, are much 
smaller than the thermometer suspended by us in the air, which, 
in this situation, seldom became more than two degrees colder 
than the atmosphere. The large branches, too, which, if fully 
exposed to the sky, would become colder than the extreme parts, 
are in a great degree sheltered by them, and, in the last place, 
the trunks are sheltered both by the larger and smaller parts, 
not to speak of the heat they derive by conduction through the 
roots, from the earth kept warm by the snow. In a similar man- 
ner is partly to be explained the way in which a layer of straw 



PROTECTION OF PLANT-HOUSES DURING COLD NIGHTS. 319 

or earth preserves vegetable matters in the fields from the inju- 
rious influence of cold during severe winters. * 

When frames and such places are covered with snow, it 
should be allowed to remain on till it melts away by the influ- 
ence of the atmosphere. In like manner, trees and shrubs 
should never have the snow drawn from their branches, during 
snow storms, except where the branches are likely to be broken 
down by the weight of snow lying upon them. Snow is not 
only the best, but also the most natural, covering during the 
winter months. 

* That the warmth of the soil acts as a protection to plants may be 
easily understood. A plant is penetrated in all directions by innumera- 
ble microscopic air-passages and chambers, so that there is a free com- 
munication between its extremities. It may, therefore, be conceived 
that, if, as necessarily happens, the air inside the plant is in motion, the 
effect of warming the air in the roots will be to raise the temperature 
of the whole individual, and the same is true of its fluids. Now, when 
the temperature of the soil is raised to 50° at noonday, by the force of 
the solar rays, it will retain a considerable part of that warmth during 
the night j but the temperature of the air may fall to such a degree, that 
the excitability of a plant would be too much and too suddenly impaired, 
if it acquired the coldness of the medium surrounding it. This is pre- 
vented by the warmth communicated to the general system, from the 
soil through the roots, so that the lowering of the temperature of the 
air by radiation during the night, is unable to affect plants injuriously 
in consequence of the antagonist force exercised by the heated soil. 



SECTION VII. 

GENERAL REMARKS ON THE MANAGEMENT OF THE 
ATMOSPHERE OF HOT-HOUSES. 

1. One of the most prevalent errors, and one of very consid- 
erable importance, consists in reversing the natural condition 
of the atmosphere in regard to the artificial regulation of the 
temperature during the night. The artificial climate is not 
rendered natural by adjusting it to the heat and light of the sun. 
In cloudy weather, and during night, the artificial atmosphere 
is kept hot by fires, and by excluding the external air; while, in 
clear days and during sunshine, fires are left off, or allowed to 
decline, the external atmosphere is admitted, and the internal 
atmosphere is reduced to the temperature of the air without. 
As heat in nature is the result of the shining of the sun, it fol- 
lows that when there is most light there is most heat ; but the 
practice in managing hot-houses is generally the reverse. 

"A gardener," observes Knight, "generally treats his plants as 
he would wish to be treated himself, and consequently, though 
the aggregate temperature of his house be nearly what it ought 
to be, its temperature during the night, relatively to that of the 
day, is almost always too high. 

" It is very doubtful if any point in exotic horticulture is less 
attended to than that which is involved in this question. We 
are too apt to forget that plants not only have their periodical 
rest of winter and summer, but they have also their diurnal 
periods of repose. Night and its accompanying refreshments 
are just as necessary to them as to animals. In all nature, the 
temperature of night falls below that of day, and thus, the great 
cause of vital excitement is diminished, perspiration is stopped, 
and the plant parts with none of its aqueous particles, although 
it continues to imbibe by all its green surface as well as by its 
roots. The processes of assimilation are suspended. No diges- 



THE ATMOSPHERE OF HOT-HOUSES. 32] 

tion of food and conversion of it into organized matter takes 
place, and instead of decomposing carbonic acid by the extrica- 
tion of oxygen, they part with carbonic acid, and rob the atmos- 
phere of its oxygen, thus deteriorating the air at night. It is, 
therefore, most important that the temperature of glass-houses 
of every kind should, under all circumstances whatever, be 
lower during the night than the minimum temperature of the 
day ; and this ought to take place to a greater extent than is 
generally imagined among practical gardeners. 

" Plants, it is true, thrive well, and many species of fruit attain 
their greatest state of perfection in some situations within the 
tropics, where the temperature in the shade does not vary in 
the day and night more than seven or eight degrees; but in 
these climates the plant is exposed during the day to the full 
blaze of the tropical sun, and early in the night it is regularly 
drenched with heavy wetting dews, and, consequently, it is very 
differently circumstanced in the day and night, though the tem- 
perature of the air in the shade, at both periods, be very nearly 
the same. I suspect," continues Knight, " that a large por- 
tion of the blossoms of the cherry and other fruit trees in the 
forcing-house often prove abortive, because they grow in too high 
and too uniform a temperature. I have been led," he says, 
" during the last three years, to try the effects of keeping up a 
much higher temperature during the day than during the night. 
As early in the spring as I wished the blossoms of my peach 
trees to unfold, my house was made warm during the middle of 
the day, but, towards night, it was suffered to cool, and the 
trees were then sprinkled, by means of a large syringe, with 
clear water, as nearly at the temperature as that which rises 
from the ground as I could obtain it, and no artificial heat was 
given during the night, unless there appeared a prospect of frost. 
Under this mode of treatment, the blossoms advanced with very 
great vigor, and, when expanded, were of a larger size than I 
had ever before seen on the same varieties. 

" Another ill effect of high night temperature is, that it exhausts 
the excitability of the tree much more rapidly than it promotes 
the growth, or accelerates the maturation, of the fruit, which 
is, in consequence, ill supplied with nutriment at the period of 



322 GENERAL REMARKS ON THE MANAGEMENT 

its ripening, when most nutriment is probably wanted. The 
Muscat of Alexandria grapes, and some other late grapes, are 
often seen to wither upon the branch in a very imperfect state 
of maturity, and the want of richness and flavor in other forced 
fruit is, we are very confident, often attributable to the same 
cause. There are few peach houses or graperies in this coun- 
try in which the night temperature does not exceed, during the 
months of April and May, that of the warmest valleys of 
Jamaica, in the hottest period of the year. And there are prob- 
ably as few hot-houses in which the trees are not more strongly 
stimulated by the close and damp air of the night, than by the 
temperature of the dry air of the noon of the following day. 
The practice which occasions this cannot be right ; it is in 
direct opposition to nature."^ 

We have fully satisfied ourselves that a high night temperature 
is injurious to plants of any description, kept under glass, and 
that green-house plants not only expand their flowers more per- 
fectly, but continue much longer in bloom, when the temperature 
of the house is reduced at night by the admission of air or other- 
wise. In like manner, fruits are not only better flavored, — a 
fact generally admitted, — but also better colored, and more per- 
fect in form, by a low temperature at night. On the other 
hand, too much air is generally admitted during the day. 

There is no doubt that gardeners frequently err in admitting 
the external air into their hot-houses, etc., during the day, par- 
ticularly in bright weather ; and this error is so common as to 
form a portion of regular practice. We have seen graperies 
and green-houses fully exposed to the parching winds of a sum- 
mer day, without screen or shelter; while the plants subjected 
to this treatment plainly indicated, by their appearance, its inju- 
rious effects. The climate of this country is so different in 
respect to its atmosphere during the day, from that of Britain, 
we are too apt to follow the practice of that country, where this 
practice is also carried to too great extent.! 

* London's Encyclopedia of Gardening. 

f The climate of the British Isles, relatively to others in the same lati- 
tude, is temperate, humid, and variable. The moderation of its temper- 
ature and its humidity are owing to its being surrounded by water, 



OF THE ATMOSPHERE OF HOT-HOUSES. 323 

The striking difference which is exhibited between our con- 
servatories and green-houses in this country, and those of Eng- 
land, is not so much owing to the existing peculiarities of cli- 
mate, as to the methods of practice adopted by the gardeners 
themselves in the management of the atmosphere of their 
houses. However costly and faultlessly a conservatory, a hot- 
house, or a grapery, may be constructed, the whole success of 
the structure depends upon the subsequent management of its 
atmosphere. 

The imitation of warm climates in winter, for the purpose of 
preserving tender plants, must not be confounded with the arti- 
ficial climate created in a hot-house for the purpose of forcing 
or accelerating foreign or native productions. As two different 
objects are sought for, different courses of procedure must be 
adopted. All that is necessary for the preservation of green- 
house plants, is to keep the atmosphere at night a few degrees 
above the freezing point ; and, indeed, if a proper attention be 
paid to the plants, so as to avoid an excess of moisture, there is 
scarcely any kind of what are generally termed hot-house plants, 
that will not thrive well enough under similar treatment. We 
have often allowed our plant-houses to fall below the freezing 
point in very severe nights; and when long and continued frosts 
set in, the plant-houses should be gradually inured to bear even 
a few degrees of frost below 32° ; and this the plants will do 
without injury, if they be kept in a proper condition. When 
the external atmosphere is dry and mild, air should be admitted 
freely to the green-house during winter, but closed early in the 

which, being less affected by the sun than the earth, imbibes less heat 
in summer, and, from its fluidity, is less early cooled in winter. As the 
sea on the coasts of Britain never freezes, its temperature must always 
be above 33° or 34° ; and hence, when air from the polar regions, at a 
much lower temperature, passes over it, that air must be in some degree 
heated by the radiation of the water. On the other hand, in summer, 
the warm currents of air from the south necessarily give out part of 
their heat in passing over a surface so much lower in temperature. 
The variable nature of its climate is chiefly owing to the unequal 
breadth of watery surface which surrounds it, — on one side a channel 
of a few leagues in breadth, on the other, the broad Atlantic Ocean. — 
{Loudon's Ency. of Gard.] 



324 GENERAL REMARKS ON THE MANAGEMENT 

afternoon, so as to preserve a portion of the warmth generated 
by the sun's rays within the house, to maintain a slight degree 
of heat in the house before the heating apparatus is set to work. 

The accelerating, or forcing, of the vegetables and fruits of 
temperate climates into a state of premature production is some- 
what different, and more difficult, than the preservation of plants 
during winter. The constitutions of the various fruit-bearing 
plants, as vines, &c, require atmospheres of different tempera- 
ture and moisture, and their success is dependent upon many 
contingent circumstances, which never occur in the mere preser- 
vation of green-house plants. 

The two principal methods of accelerating fruits in hot- 
houses are, by planting them permanently in borders prepared 
for them, and by planting in tubs and large pots ; and keeping 
a succession of plants thus prepared, every year, to supply the 
places of those which had become unfruitful by the effects of 
forcing and producing a heavy crop of fruit. 

The first of these methods has long been practised, and is, 
undoubtedly, the best for permanent crops, as more fruit can be 
produced in a house by this method than by the potting system. 
When once planted out, however, and growing under the glass, 
they cannot be removed from the house, and, consequently, are 
dependent upon the cultivator for the elements of consumption, 
air and water. The grand effect is produced by heat, and the 
great aim is to supply just as much as will harmonize with the 
light afforded by the sun, and the peculiar condition under which 
the plants exist. All the operations must be natural and grad- 
ual, and a good cultivator will always follow the dictates and 
example of the natural world. He will never be anxious to force 
things on too rapidly, — a very common error, and a frequent 
cause of failure ; he will likewise be careful to guard against 
sudden checks, either by a sudden decrease of temperature, or 
the reverse ; but he will endeavor to continue the natural course 
of vegetation uninterruptedly through foliation, inflorescence, and 
fructification. 

The skilful balancing of the temperature and moisture of the 
air, in cultivating the different kinds of fruits in forcing-houses, 
and the just adaptation of the various seasons of growth and 



OF THE ATMOSPHERE OF HOT-HOUSES. 325 

maturity, constitute the most complicated and difficult part of 
the gardener's art. There is some danger in laying down any 
general rules on this subject, so much depends upon the pecu- 
liarities of the kind under cultivation, and the endless train of 
considerations connected with the process of forcing. 

The following rules, however, may be safely stated, as deserv- 
ing especial attention from the gardener in charge of hot-houses : 

1. Moisture is most required in the atmosphere by plants 
when they first begin to grow, and least when their periodical 
growth is completed. 

2. The quantity of atmospheric moisture required by plants 
is, ccsteris paribus, in inverse proportion to the distance from the 
equator of the countries which they naturally inhabit. 

3. Plants with annual stems require more than those with 
ligneous stems. 

4. The amount of moisture in the air most suitable to plants 
at rest, is in inverse proportion to the quantity of aqueous matter 
they, at that time, contain. Hence the dryness required in the 
atmosphere, by succulent plants, when at rest. 

Moisture in the atmosphere, then, is absolutely necessary to 
all plants, when they are in a state of rapid growth, partly be- 
cause it prevents the action of perspiration becoming too violent, 
as it always does in a high and dry atmosphere, and partly 
because, under such circumstances, a considerable quantity of 
aqueous food is absorbed from the atmosphere, in addition to 
that drawn from the soil by the roots. 

Excessive moisture is injurious to vegetables in winter, when 
their digestive and decomposing powers are feeble, and evapora- 
tion from the soil should rather be intercepted than otherwise, 
except when the atmosphere is dried to an unhealthy degree, 
by the use of fire heat. 

One of the causes of the Dutch method of winter-forcing is, 
undoubtedly, their avoiding the necessity of winter ventilation, 
by intercepting the excessive vapor that rises from the soil, and 
would otherwise mix with the air. For this purpose they inter- 
pose screens of oiled paper between the earth and the air of their 
houses ; and in their pits for vegetables, they cover the surface 
of the ground with the same oiled paper, by which means vapor 



326 GENERAL REMARKS ON THE MANAGEMENT 

is effectually intercepted, and the atmosphere preserved from 
excessive moisture. 

The difficulty of keeping succulent plants in damp cellars, 
during winter, is also owing to the same cause. Moisture, 
without a sufficiency of light to enable plants to decompose it, 
quickly destroys them. 

On the other hand, the difficulty of keeping up that necessary 
degree of humidity in the atmosphere of a dwelling room, dur- 
ing the summer months, is the cause of the unhealthiness of 
plants kept in them ; and the fact of their position being gener- 
ally in the window, where there is always a current of air from 
without, during the day, contributes, in a great measure, to 
exhaust the plants of their contained moisture, and then they 
gradually decline. Could the atmosphere around them be kept 
sufficiently moist, with plenty of light, there is no reason why 
they should not thrive as well as in the green-house. 

We have already alluded to the injurious effects of maintain- 
ing a high temperature in green-houses and conservatories dur- 
ing winter. If we look over the different climates of the world, 
we shall find, that in each there is a season of growth, and a 
season in which vegetation is more or less suspended, and that 
these periodically alternate with the same regularity as our 
summer and winter. I do not know that in nature there is any 
exception to this rule ; for even in the Tierra Templada of Mex- 
ico, where, it is said, that, at the height of 4000 to 5000 feet, 
there constantly reigns the genial climate of spring, which does 
not vary more than 8° or 9° of temperature, — intense heat and 
excessive cold being alike unknown, — the mean temperature 
varying from 68° to 70°; we cannot suppose that, even in 
that favored region, a season of repose is wanting; for it is 
difficult to conceive how plants can exist, any more than animals, 
in a season of incessant excitement. Indeed, it is pretty evident 
that these countries have periods when vegetation ceases, for 
Xalapa belongs to the Tierra Templada, and we know that the 
Ipomea purga, an inhabitant of its woods, dies down annually, 
like our native Convolvuli. 

From what has already been said on this subject, it is evident 
that the natural resting of plants from growth is a most impor- 



OF THE ATMOSPHERE OF HOT-HOUSES. 327 

tant phenomenon, of universal occurrence, and that it takes place 
equally in the hottest and in the coldest regions. It is, there- 
fore, a condition necessary to the well-being of a plant, not to 
be overworked, under any circumstances whatever ; and there 
cannot be any good gardening where this is not attended to, in 
the management of plants under glass. Rest is effected in two 
ways ; either by a very considerable lowering of temperature, 
or by a degree of dryness under which vegetation cannot be 
sustained. 

In treating on the various conditions of the atmosphere, and 
its effects on vegetation, .we have already sufficiently explained 
these influences ; which renders it unnecessary to recapitulate 
them in this place. In practice we find that the effects of a 
very dry atmosphere are, necessarily, an inspissated state of the 
sap of the plant, and this, in all cases, — if not carried to an 
injurious extent, — leads to the formation of blossom-buds, and 
of fruit. This influence, however, must be controlled by the 
cultivator, otherwise it will lead to inevitable failure, as the sap 
of the plant may be so much dried up as to prevent its accumu- 
lation in sufficient quantity, in the smaller branches, to form 
fruit buds. It is, nevertheless, true, that a low temperature, 
under the influence of much light, by retarding and diminishing 
the expenditure of the sap in growing plants, produces nearly 
similar effects, and causes an early appearance of fruit. 

All the operations may be very essentially influenced by these 
facts, when they are fully understood to the cultivator, and, by 
a skilful alteration of the periods of rest, we are enabled to 
break in upon the natural habits of plants, and to invert them 
so completely, that the flowers and fruits of summer may be 
brought to perfection at the opposite season of the year. 

By carrying out these principles, we have, for several years, 
succeeded in fruiting grape-vines in the months of March and 
April, without any extraordinary degree of excitability being 
exercised at any period of their growth. The whole secret of 
success consists in preparing the plants the preceding season, 
by ripening their wood at an early period of the season, and ex- 
posing them to such an amount of heat and dryness as can be ob- 
tained by presenting them, unwatered, to the influence of the sun, 
28* 



328 GENERAL REMARKS, ETC. 

at an early period of summer ; then, after the leaves have ripened, 
keep them as cool as possible for some time ; thus causing a 
sufficient accumulation of excitability by the end of October, 
instead of the following month of May, at which period the fruit 
will be ripe. 



SECTION VIII. 

VENTILATION WITH FANS. 

In a preceding part of this work, [see Part II., Sec.V.] we have 
described a method of warming hot-houses practised in Ger- 
many, in which a fan is used as a means of propelling the 
heated air into the apartments required to be warmed, and by 
which the volume of air to be heated is drawn from the external 
atmosphere. As an auxiliary to a heating apparatus, however, 
the complicated arrangements of this machine, the cost of its 
construction, and the expense and trouble of working it, must 
ever continue to prevent its adoption as a method of warming 
horticultural buildings, however extensive they may be. But as 
an auxiliary of ventilation, and as a means of creating that con- 
tinual motion in the air, which some cultivators so much admire, 
it is undoubtedly superior to all other methods. 

Fans are so common as to require very little description. The 
kind of machine generally used for this purpose is merely a 
light circular kind of wheel, composed of as many vanes or blades 
as the size will admit. By the constant revolution of this wheel, 
a movement is created in the atmosphere, which causes a change 
in the position of the atomic particles of the atmosphere of the 
room in which it is at work ; but does not, as some suppose, 
tend to its equalization. 

Fans are of two kinds, and have different methods of action. 
The one is termed blowing fans ; the other, exhausting, or suction 
fans. In the first case, the air in the house is driven outwards 
from, the fan, or blown away ; in the other, it is drawn towards it. 
It will appear evident, however, that, in applying this machine 
to the creation of a movement in the atmosphere of a hot-house, 
various requisites must be had, namely, a moving power, con- 
stantly and steadily acting, and completely under control ; and 
when it is to be applied to night ventilation and motion, which 
appears to us the most adaptable use to which it can be applied 



330 



VENTILATION WITH FANS. 



in relation to any kind of horticultural structures, then a supply 
of warmed air must be kept up by means of the heating appa- 
ratus, and a channel of conduction for the vitiated air to 
escape by. 

In places where the mechanical power for moving a fan can 
be easily obtained, this machine may be turned to excellent 
advantage. The question, therefore, is not as to the adaptability 
of the machine, but as to the means of working it so as to bring 
it within the reach of hot-house adaptation, at a cost which 
would justify us in recommending it. 

There are various points to be considered in relation to draw- 
ing in fresh, and expelling foul, air from a hot-house, namely, that 
we must not only expel the vitiated air from the house, but we 
must introduce pure air into its place ; and that pure air must 
be warmed before it is introduced. We have heard and read a 
good deal about this and the other method of introducing warm 
air into a hot-house ; and, in theory, many of these notions are 
very plausible, but when we come to apply them to practice, 
they are entire failures. 

The principal objects to be obtained by an efficient system of 
night ventilation may be classed as follows : — 

1. The expulsion of a certain quantity of vitiated air, in a 
eertain time, from the whole volume contained in the house ; 
and, as the impure air rises by rarefaction to the upper regions 
of the house, means must be provided to carry it away, with- 
out creating counter-currents, or admitting any cold air, by the 
channels of conduction thus made. 

2. A quantity of air must be introduced to the internal vol- 
ume equal to the quantity expelled ; otherwise the remaining 
internal volume will expand, by its increased temperature, and 
fill the space occupied by the decreasing volume, and thus the 
air becomes more vitiated than if none had escaped. The air 
thus brought in must be introduced without acting in a direct 
current upon the vegetable productions within the house. 

3. The air thus introduced must be warmed to a certain tem- 
perature, before it enters the house. This temperature should 
be regulated by the temperature at which it is desired to main- 
tain the internal atmosphere. If the desired temperature be 



VENTILATION WITH FANS. 331 

50°, the air entering should not be under that temperature, but 
rather a few degrees above it. 

4. If the house be heated by pipes laid round the side of the 
house, the air thus admitted should be introduced so as to pass 
upward, by the side of the pipes, on entering the house. This 
air should pass regularly and consentaneously upwards ; not in 
sudden blasts and currents, which have always an injurious 
influence on the internal atmosphere. 

To effect this, a hot-air chamber should be placed in connec- 
tion with the heating apparatus, from which must be laid air 
channels, or conduction tubes, all around the house, having 
apertures for the egress of the air, at distances of six or eight feet 
apart. Within this chamber a fan might be used for drawing 
in the external air and driving in the warmed air through the 
tube. This fan might be driven by a small windmill con- 
structed for the purpose. 

When air is under the control of a moving power, it will take 
any direction that is desired. It will move horizontally, or ver- 
tically, either upwards or downwards, and even in both direc- 
tions, at the same time. 

It is essential, however, that the supply to be warmed should 
be drawn from the external atmosphere ; and here the fan may 
be used to great advantage. In no case should the supply of air 
be drawn from the interior of the house. The vitiated air, as it 
passes upward, should be allowed to pass off freely into the 
atmosphere. 

In this country, however, the fan cannot be so advantageously 
applied in the ventilation of horticultural buildings, as in north- 
ern Europe, and only at night, the period when ventilation is 
most needful. The large amount of artificial heat necessary in 
our New England climate, in severe nights, is more injurious to 
green-house plants than the excessive heat of summer. There 
is no impossibility, however, in producing a constant and equa- 
ble motion in the atmosphere of green-houses, at night ; and 
this may be effected by the means which we have just ex- 
plained. 

Fans may also be beneficially employed in producing a cool- 
ing effect in the air at the top of the house. The injurious 



332 VENTILATION WITH FANS. 

effect of the highly-heated air in the upper regions must be 
obvious. We have measured the temperature of a house 45 
feet in height, and have found the temperature at the floor of the 
house to be 38°, while the temperature of the upper stratum was 
103°, showing a difference of 65°. In many other cases, we 
have found the temperature of the upper stratum of air in a 
house, above 120°, while the water cistern, at the floor of the 
house was covered with ice. The application of a fan may be 
beneficial in reducing this temperature, and expelling the foul 
air collected in the upper portions, at apertures lower down the 
house. 

Various other mechanical contrivances, besides the fan, have 
been used for producing motion in the atmosphere of houses. 
Among these may be mentioned common windmills, of which 
we have already spoken. The windmill ventilator is a very 
adaptable machine, and may be constructed very simply, in con- 
nection with a hot-house, and applied in moving the atmosphere 
of the house, or in propelling the warmed air through the con- 
duction tubes with greater velocity than it would acquire by its 
own specific gravity. The windmill, of course, is turned by 
the force of the wind outside the house, and is entirely depend- 
ent upon the motion of the external air, for the power it exer- 
cises over the internal atmosphere. In hot-houses, with dome- 
shaped roofs, it is well adapted for drawing off the highly- 
heated air at the top of the house, and may be made something 
like the screw propeller of the steamboats, and situated directly 
in the apex of the roof. 

Pumps have also been used for drawing off the foul air from 
buildings, although we are not aware that they have ever been 
employed for ventilating hot-houses, for which they are not at 
all adapted. 

Chimney shafts are well adapted for producing motion in the 
air, by the draughts. None of these methods, however, are so 
useful as the fan, when mechanical means are to be applied ; 
though, for the practical purposes of ventilation, in horticultural 
structures, the common process of spontaneous ventilation must, 
in general cases, suffice ; — and, therefore, the question is, as to 
the means of admitting the air, and the temperature at which it 



VENTILATION WITH FANS. 333 

is to be admitted. The movements of the atmosphere, caused 
by the difference of temperature between the external and inter- 
nal volumes, have been already considered ; and we now leave 
the subject to the consideration of those who are engaged in the 
practical operations of exotic horticulture. 



APPENDIX 



TABLE I. 



TABLE of the Expansive Force of Steam, in Atmospheres, and in lbs. 
per square inch ; for temperatures above 212° of Fahrenheit. 

N. B. The steam is supposed to be in contact with the water from which it is formed, 
and the water and steam to be alike in temperature. 



m 

<0 «J 


Pressure. 


OJ .J 


Pressure. 


m 


Pressure. 


Oj ■ — 


03 




boja 


m 




bnxi 






P | 


10 




O 03 








<D 




— a 


J3 


lbs. 




a* 
w 

o 


lbs. 


GJ2 
— «S 

3 fe 


a, 

O 


lbs. 


8 ° 


s 
< 






< 






s 
■3 




212 


1 . 


15 


431 


23 


345 


646 


150 


2250 


251 


2 


30 


436 


24 


360 


655 


160 


2400 


275 


3 


45 


439 


25 


375 


663 


170 


2550 


294 


4 


60 


457 


30 


450 


671 


180 


2700 


308 


5 


75 


473 


35 


525 


679 


190 


2850 


320 


6 


90 


487 


40 


600 


686 


200 


3000 


332 


7 


105 


499 


45 


675 


694 


210 


3150 


342 


8 


120 


511 


50 


750 


700 


220 


3300 


351 


9 


135 


521 


55 


825 


707 


230 


3450 


359 


10 


150 


531 


60 


900 


713 


240 


3600 


367 


11 


165 


540 


65 


975 


719 


250 


3750 


374 


12 


180 


549 


70 


1050 


726 


260 


3900 


381 


13 


1V5 


557 


75 


1125 


731 


270 


4050 


387 


14 


210 


565 


80 


1200 


737 


280 


4200 


393 


15 


225 


572 


85 


1275 


742 


290 


4350 


399 


16 


M0 


579 


90 


1350 


748 


300 


4500 


404 


17 


255 


586 


95 


1425 


753 


310 


4650 


409 


18 


270 


592 


100 


1500 


758 


320 


4800 


414 


19 


285 


605 


110 


1650 


763 


330 


4950 


418 


20 


300 


616 


120 


1800 


768 


340 


5100 


423 


21 


315 


627 


130 


1950 


772 


350 


5250 


427 


22 


330 


636 


140 


2100 









* # # The above Table is deduced from the experiments of MM. 
Dulong and Arago. Their calculations extend only as far as 50 atmos- 
29 



336 



APPENDIX. 



pheres ; from thence the pressures are now calculated to 350 atmos- 
pheres by their formula, viz. : — 

t= s/e— 1 
•7153 
where e represents the pressure in atmospheres, and t the temperature 
above 100° of Centigrade. In this equation each 100° of Centigrade is 
represented by unity. 

In reducing these temperatures from Centigrade to Fahrenheit's scale, 
vhere the fractions amount to -5, they have been taken as the next 
legree above, and all fractions below -5 have been rejected. 



TABLE II. ; 

TABLE of the quantity of Vapor contained in Atmospheric Air, at 
different Temperatures, when saturated. 





-_o 


1 


o 




o 




3 ^ 




3 . 




3 ^ 


li 


O Jp 


c 


^"S 


c 


q(g 


< 


u 'S 


< 




£j 


m 3 


o 


ft^ 


o 


03 ►? 


v. 
O 


% 


03 

3 
03 


u 2 


03 
3 

6 

03 


o ™ 
P..5 

^5 


03 

3 

03 


Co 


&, 


c.S 


a, 


O a 


a. 


9 a 


g 


x'~ 


s 


X'~ 


1 


' Eji~L 


u 


1§ 


03 




H 






<y 




6* 




a 


20° 


1-52 


48 3 


3-98 


76° 


9-53 


22 


1-64 


. 50 


4-24 


78 


10-16 


24 


1-76 


52 


4-52 


80 


10-78 


26 


1-90 


54 


4-82 


82 


11-49 


28 


2-03 


56 


5-13 


84 


12-20 


30 


2-25 


58 


5-51 


86 


12-91 


32 


2-32 


60 


5-83 


88 


13-61 


34 


2-48 


62 


6-21 


90 


14-42 


36 


2-64 


64 


6-60 


92 


15-22 


38 


2-82 


66 


7-00 


94 


16-11 


40 


3-02 


68 


7-43 


96 


17-11 


42 


3-24 


70 


7-90 


98 


18-20 


44 


3-48 


72 


8-40 


100 


19-39 


46 


3-73 


74 


8-95 







* # * The above Table is computed from Dr. Dalton's Experiments on 
the Elastic Force of Vapor. 



APPENDIX. 



337 



TABLE III. 

TABLE of the Expansion of Air and other Gases by Heat, when per- 
fectly free from Vapor. 



Temperature 




Temperature 




Fahrenheit's 


Expansion. 


Fahrenheit's 


Expansion. 


Scale. 




Scale. 




32° 


1000 


100° 


1152 


35 


1007 


110 


1178 


40 


1021 


120 


1194 


45 


1032 


130 


1215 


50 


1043 


140 


1235 


55 


1055 


150 


1255 


60 


1066 


160 


1275 


65 


1077 


170 


1295 


70 


1089 


180 


1315 


75 


1099 


190 


1334 


80 


1110 


200 


1354 


85 


1121 


210 


1372 


90 


1132 


212 


1376 


95 


1142 







* # * The above numbers are obtained from Dr. Dalton's experiments, 
which give an average of ^^ part, or -00207 for the expansion by each 
degree of Fahrenheit. Gay Lussac found it to be equal to ^-^ part, or 
'002083 for each degree of Fahrenheit; and that the same law extends 
to condensable vapors when excluded from contact of the liquids which 
produce them. 



33S 



APPENDIX. 



TABLE IV. 

TABLE of the Specific Gravity and Expansion of Water at different 
Temperatures. 



% 


a 

o 




Weight 


Si 


s 




Weight 






Specific 


of 
1 Cubic 




fl 


Specific 


of 

1 Cubic 


sll 


a, 


Gravity. 


Inch, 


05 £ 


04 


Gravity. 


Inch, 


s as 


W 




ingrains. 


1 £ 


H 




in grains. 


30° 








H U 








•00017 


•9998 


252-714 


121° 


•01236 


•9878 


249-677 


32 


•00010 


•9999 


252-734 


124 


•01319 


•9870 


249-473 


34 


•00005 


•9999 


252-745 


127 


•01403 


■9861 


249-265 


36 


•00004 


•9999 


252-753 


130 


•01490 


•9853 


249-053 


38 


•000002 


•9999 


252-758 


133 


•01578 


•9844 


248-836 


39 


•00000 


1-0000 


252-759 


136 


•01668 


•9836 


248615 


43 


•00003 


•9999 


252-750 


139 


•01760 


•9827 


248-391 


46 


•00010 


•9999 


252-734 


142 


•01853 


•9818 


248-163 


49 


•00021 


•9997 


252-704 


145 


•01947 


•9809 


247-931 


52 


•00036 


•9996 


252-667 


148 


•02043 


•9799 


247-697 


55 


•00054 


•9994 


252-621 


151 


•02141 


•9790 


247-459 


58 


•00076 


•9992 


252-566 


154 


•02240 


•9780 


247-219 


61 


•00101 


•9989 


252-502 


157 


•02340 


•9771 


246-976 


64 


•00130 


•9986 


252-429 


160 


•02441 


•9760 


246-707 


67 


•00163 


•9983 


252-349 


163 


•02543 


•9751 


246-483 


70 1 


•00198 


•9981 


252-285 


166 


•02647 


•9741 


246-233 


73 1 


•00237 


•9976 


252-162 


169 


•02751 


•9731 


245-982 


76 


•00278 


•9972 


252-058 


172 


•02856 


•9721 


245-729 


79 


•00323 


•9967 


251-945 


175 


•02962 


•9711 


245-474 


82 1 


•00371 


•9963 


251-825 


178 


•03068 


•9701 


245-218 


85 i 


•00422 


•9958 


251-698 


181 


•03176 


•9691 


244-962 


88 


•00476 


•9952 


251-564 


184 


•03284 


•9681 


244-704 


91 


•00533 


•9947 


251-422 


187 ' 


•03392 


•9671 


244-446 


94 


•00592 


•9941 


251-275 


190 ; 


•03501 


•9660 


244-187 


97 


•00654 


•9935 


251121 


193 


•03610 


•9650 


243-928 


100 


•00718 


•9928 


250-960 


196 ! 


•03720 


•9640 


243-669 


103 


•00785 


•9922 


250-794 


199 


•03829 


•9630 


243-410 


106 


•00855 


•9915 


250-621 


202 i 


•03939 


•9619 


243-151 


109 


•00927 


•9908 


250-443 


205 


•04049 


•9609 


242-893 


112 


•01001 


•9901 


250-259 


208 


•04159 


•9599 


242-635 


115 


•01077 


•9893 


250-070 


212 


•04306 


•9585 


242-293 


118 


•01156 


•9885 


249-876 











# # # In the above Table the expansions are calculated by Dr. Young's 
formula, 22 / 2 (1 — -002/) in ten millionths. The diminution of specific 
gravity is calculated by this equation: -0000022/ 2 — -00000000472/3. 
In both equations, / represents the number of degrees above or below 
39° of Fahrenheit. The absolute weight of a cubic inch of water, at 
any temperature, may be found by multiplying the weight of a cubic 
inch at 39°, by the specific gravity at the required temperature. 



APPENDIX. 



339 



TABLE V. 

TABLE of the Specific Heat, Specific Gravity, and Expansion by Heat, 

of different Bodies. 

Barometer 30 Inches. — Thermometer 60°. 



Air (atmospheric) 
— (dry). . . . 
Aqueous vapor . 

Azote 

oxide of . . 

Carbonic acid 

oxide . 



Hydrogen 
Olefiant gas 
Oxygen . . 
Water . . . 



Water . 
Bismuth 
Brass . 



wire 

Cobalt 

Copper 

Gold 

Glass (flint) 

(tube) ..... 

Iron (cast) 

(bar) 

Lead 

Nickel 

Pewter (fine) 

Platinum ...... 

Silver 

Solder (lead 2 -f- tin 1) 
Spelter (brass 2-j-zinc l) 
Steel (untempered) . . 
— (yellow tempered) 

Sulphur 

Tellurium 

Tin 

Zinc , 



Specific Heat. 



3 •§ Specific 
£ ___ p gravity 



O Pu, 



•2669 
•2767 
•8470 
•2754 
•2369 
•2210 
•2884 

3-2936 
•4207 
•2361 

1-000 



1-000 

•0288 



1498 
0949 
0298 



1100 
0293 
1035 



0314 
0557 



1880 
0912 
0514 

0927 



1-000 

'■633 

•9722 

1-5277 

1.5277 

•9722 

•0694 

•9722 

1-1111 



Weight of 

100 Cubic 

Inches. 



■a o 



Grains. 

30-519 

19 : 321* 

29-65 
46-596 
46-596 
29-65 

2-118 
29-65 
33-888 



1-000 

9-880 
7-824 
8-396 
8-600 
8-900 

19-250 
2-760 
2-520 
7-248 
7-788 

11-350 
8-279 



21-470 
10-470 



7-840 
7-816 
1-990 
6-115 
7-291 
7-191 



Ounces. 

57-87 
571-7 
452-77 
485-87 
497-6 
515-0 
1114-0 
159-72 
145-83 
418-9 
450-2 
656-8 
478-5 

1242-4 
605-8 



453-7 

452-31 

115-1 

353-5 

421-9 

4160 



Linear Ex- 
pansion by 

180° of heat; 
from 

32o to 21 2o. 



00186671 
00193000 

00172244 
00146606 
00081166 
00087572 
00111111 
00122045 
00284836 

00228300 
00099180 
00208260 
00250800 
00205800 
00107875 
00136900 



00217298 
00294200 



# # # Air is taken as the standard for the specific gravity of the gases, 
and water as the standard for the solids. 
* Specific gravity of steam at 212° = -481. Weight of 100 cubic inches, 14-680 grains. 

29* 



340 



APPENDIX. 



TABLE VI. 

TABLE of the Effects of Heat. 




Greatest heat observed 

Hessian crucible fused 

Cast iron thoroughly melted 

Greatest heat of a smith's forge 

" " of a plate-glass furnace . . . 
" " of a flint-glass ditto .... 

Derby porcelain vitrifies 

Welding heat of iron (greatest) 

" " " " (least) 

Fine gold melts 

Fine silver melts 

Swedish copper melts 

Brass melts 

Diamond burns 

Red heat fully visible in daylight .... 

Iron red-hot in the twilight 

Charcoal burns 

Heat of a common fire 

Iron bright-red in the dark 

Zinc melts (680° Davy) 

Mercury boils (Black 600°) (Secondat 644°) Petit and 

Dulong) 

" " (Crichton 655°) (Irvine 672°) (Dalton) . . 

Lowest ignition of iron in the dark 

Lead melts (Guyton and Irvine 594°) (Crichton) . . . . 
Steel becomes dark blue, verging on black 

" " a full blue 

Sulphur burns . 

Steel becomes a bright blue 

" " purple 

" " brown, with purple spots 

" " brown 

Bismuth melts 

Steel becomes a full yellow 

" " a pale straw color 

Tin melts 

Steel becomes a very faint yellow 

Tin 3 -f- lead 2 -j- bismuth 1, melts . . 

Tin and bismuth, equal parts, melts 

Bismuth 5 -{-tin 3 -(-lead 2, melts 

Water boils (barometer 30 in.) . . . ■. . 

Water freezes . . 

Milk freezes . . . 

Vinegar freezes 

Sea water freezes 

Strong wine freezes . . • 

Quicksilver congeals 

Sulphuric aether congeals 

Natural temperature at Hudson's Bay 

Great artificial cold 



Fahrenheit's 
Scale. 

25127 

20557 

20577 

17327 

17197 

15897 

15637 

13427 

12777 

5237 

4717 

4587 

3807 

2897 

1077 

884 

802 

790 

752 

700 

656 

660 

635 

612 

600 

560 

560 

550 

530 

510 

490 

476 

470 

450 

442 

430 

334 

283 

212 

212 

32 

30 

28 

28 

20 

—39 

—47 

—51 

—91 



APPENDIX. 



341 



TABLE VII. 

TABLE of the Quantity of Water contained in 100 feet of Pipe of dif- 
ferent diameters. 



Diameter 


Contents of 100 Feet 


of Pipe. 


in length. 


Inches. 


Gallons. 


h 


•84 


1 


3-39 


H 


7-64 


2 


13-58 


2£ 


21-22 


3 


30-56 


4 


54-33 


5 


84-90 


6 


122-26 



TABLE VHI. 

TABLE, showing the Effects of Wind in Cooling Glass. 



Velocity 

of the 

wind 

in miles 

per hour. 


Time of cooling the Thermometer 20°, from 120° to 100°, 
. . Fahrenheit. 


Observed 
time of 
cooling. 


Time re- 
duced to 
decimals 


Corrected time, being the inverse of the square 
root of the velocities, in decimals of a minute. 




minute. 




3-26 


2' 35" 


2-58 


2-58 


5-18 


2 10 


2-16 


204 


6-54 


1 55 


1-91 


1-82 


8-86 


1 40 


1-66 


1-56 


10-90 


1 30 


1-50 


1-41 


13-36 


1 15 


1-25 


1-27 


17-97 


1 5 


1-08 


1-10 


20-45 


1 


1-00 


1-03 


24-54 


55 


•91 


•94 


27-27 


48 


•81, 


•88 



342 



APPENDIX. 



TABLE IX. 

Experiments on the Cooling Effect of Windows.* 

These experiments were made in a wooden house, double plastered, 
with a space between the two plasterings ; walls 6 inches thick. Heat 
introduced from a hot-air furnace, heated air being shut off when the 
room was heated to a proper temperature. Thermometer four feet from 
the floor. When the windows were closed, two thicknesses of blankets 
were fastened closely to the window-frame internally. 

Three windows, equal to 33-21 square feet ; walls, 531 square feet ; 
cubic contents of room, 1930 feet, being 9 feet high, 16-5 feet long, 13 
feet wide. 

The room was kept as nearly as possible under the same circum- 
stances. 

Time. 



March 19, 1843. 26 
25 



External Internal 
Thermom. Thermom. 
o 

74 
64 



h. m. 

9 1 

10 15 



Weather calm, windows 
uncovered. 



March 20. 



March 21. 



22 

18 



25 
24£ 



24 
22 



17 
16 



74 
59 



74 

64 



74 
61 



74 
64 



74 
64 



74 

11 41 
2 5 


144 

8 8 

9 24 


76 

10 17 

12 22 


125 

8 51 
10 19 


88 

11 26 

12 16 



Windows covered 
blankets. 



with 



Windows uncovered. 



Windows covered 
blankets. 



with 



Calm, windows covered. 



Windows uncovered, 
calm. 



50 



The experiments were also made in other rooms, with wooden shut- 
ters internally. 

The results are as follows : — 

1st, room cooled 10° in 74' = 1° in 7-4', windows open. 
" " 15° in 144' = 1° in 9-6', windows closed. 

2d, room cooled 10° in 76' = 1° in 7-6', windows open. 



* Wyman on Ventilation. 



APPENDIX. 343 

2d, room cooled 13° in 125' = 1° in 9-6', windows closed. 
3d, room cooled 10° in 88' = 1° in 8-8', windows closed. 
" " 10° in 50' = 1° in 5-0', windows open. 

Experiment with wooden shutters : — 
Room cooled 10° in 93' = 1° in 9-3', shutters closed. 
" " 10° in 58' — 1° in 5-8', shutters open. 

From the above, the effect of glass is very evident, and also the advan- 
tage of curtains and shutters. We shall not attempt to form any gen- 
eral rule, since it could be applied correctly only under circumstances 
which differed very little from the above. 

The preparation for covering white cotton for interior windows is 
composed of 4 oz. of pulverized dry white cheese, 2 oz. of white slack 
lime, and 4 oz. of boiled linseed oil. These three ingredients having 
been mixed with each other, 4 oz. of the white of eggs, and as much of 
the yolk, are added, and the mixture then made liquid by heating. 
The oil combines easily with the other ingredients, and the varnish re- 
mains pliable and quite transparent. It is applied with a brush. 



344 



APPENDIX. 



TABLE X. 

Weights of "Watery Vapor in one Cubic Foot of Air, at Dew-points from 
0° to 100° Fahrenheit. 



03 aj 

n.-S 
- fa 


B3 

.£ 
- o 


P J: 
top 

03 — 

: fa 


.£ 
2 o 

ci 

O 


03 b 

fa 


C 

2 o 

6 


g'3 

feE 03 

«| 
fa 


S3 

jl 





0-186" 


26 


1-915 


51 


4-382 


76 


9-523 


1 


810 


27 


1-986 


52 


4-524 


77 


9-813 


2 


0-836 


28 


2-054 


53 


4-671 


78 


10-111 


3 


0-864 


29 


• 2-125 


54 


4-822 


79 


10-417 


4 


0-893 


30 


2-197 


55 


4-978 


80 


10-732 


5 


0-925 


31 


2-273 


56 


5-138 


81 


11-055 


6. 


0-957 


32 


2-350 


57 


5-303 


82 


11-388 


7 


0-992 


33 


2-430 


58 


5-473 


83 


11-729 


8 


1-028 


34 


2-513 


59 


5-648 


84 


12-079 


9 


1-065 


35 


2-598 


60 


5-828 


85 


12-439 


10 


1-103 


36 


2-686 


61 


6-013 


86 


12-808 


11 


1-143 


37 


2-776 


62 


6-204 


87 


13-185 


12 


1-184 


38 


2-870 


63 


6-400 


88 


13-577 


13 


1-226 


39 


2-966 


64 


6-602 


89 


13-977 


14 


1-270 


40 


3-066 


65 


6-810 


90 


14-387 


15 


1-315 


41 


3-168 


66 


7-024 


91 


14-809 


16 


1-361 


42 


3-274 


67 


7-243 


92 


15-241 


17 


1-409 


43 


3-382 


68 


7-469 


93 


15-684 


18 


1-459 


44 


3-495 


69 


7-702 


94 


16-140 


19 


1-510 


45 


3-610 


70 


7-941 


95 


16-607 


20 


1-563 


46 


3-729 


71 


8-186 


96 


17-086 


21 


1-618 


47 


3-851 


72 


8-439 


97 


17-577 


22 


1-674 


48 


3-979 


73 


8-699 


98 


18-081 


23 


1-733 


49 


4-109 


74 


8-966 


99 


18-598 


24 


1-793 


50 


4-244 


75 


9-241 


100 


19-129 


25 


1-855 















APPENDIX. 



345 



TABLE XI. 

Dalton's Table of the Force of Vapor, from 32° to 80°. 



Tempe- 
rature. 


Force of va- 
por in inches 
of mercury. 


Tempe- 
rature. 


Force of va- 
por in inches 
of mercury. 


Tempe- 
rature. 


Force of va- 
por in inches 
of mercury. 


32° 


0-2000 


49° 


0-3483 


65 


0-6146 


33 


0-2066 


50 


0-3600 


66 


0-6355 


34 


0-2134 


51 


0-3735 


67 


0-6571 


35 


0-2204 


52 


0-3875 


68 


0-6794 


36 


0-2277 


53 


0-4020 


69 


0-7025 


37 


0-2352 


54 


0-4171 


70 


0-7260 


38 


0-2429 


55 


0-4327 


71 


0-7507 


39 


0-2509 


56 


0-4489 


72 


0-7762 


40 


0-2600 


57 


0-4657 


73 


0-8026 


41 


0-2686 


58 


0-4832 


74 


0-8299 


42 


0-2775 


59 


0-5012 


75 


0-8581 


43 


0-2866 


60 


0-5200 


76 


0-8873 


44 


0-2961 


61 


0-5377 


77 


0-9175 


45 


0-3059 


62 


0-5560 


78 


0-9487 


46 


0-3160 


63 


0-5749 


79 


0-9809 


47 


0-3264 


64 


0-5944 


80 


10120 


48 


0-3372 











Note to Table XII. — (See next page.) 

To determine the dew-point, take two thermometers, the scales of 
which agree, cover the bulb of one with thin muslin, and wet it with 
water ; swing both thermometers in the air, that they may be exposed under 
similar circumstances, and note the height of the mercurial column in 
each, after it has become stationary. Ascertain the difference between the 
heights of the two columns. In the following table, find a number at the 
top corresponding to the difference of heights, and in the left hand 
column the degree answering to the temperature indicated by the dry 
bulb thermometer ; the figure at the intersection of the two lines is the 
dew-point. 

Suppose, for instance, the dry bulb indicated 70°, and the wet bulb 
61° ; ,70 — 61 = 9, which is found at the top of the table ; in the column 
beneath, and against 70°, is 55° , the dew-point. 



346 



APPENDIX. 



TABLE XII. 



Table for ascertaining Dew-point by 



Temp. 

of air 


1 


2 


3 


4 


5 


6 17 


8 1 9 


1 10 1 11 


12 13 


14 


90- 


88-7 


875 


81V3 


85-1 


83-8 


82-581-2 


Wf&h 


772175^ 


tR Wo 


71-5 


89 


87-7 


86-5 


85-3 


84-0 


82-7 


81-480-1 


78-8,774 


76-074-6 


73-2 71-8 


70-3 


88 


86-7 


85-5 


84-3 


83-0 


81-7 


80-4;79-l 


77776-3 


74-9 73-£ 


72-170-6 


69-1 


87 


85-7 


84-5 


83-2 


81-9 


80-6 


79-3:78-0 


76-6 75-2 


73-872-4 


70-9 69-4 


67-9 


86 


84-7 


83-5 


82-2 


80-9 


79-6 


78-2j76-9 


75-574-1 


72-771-2 


69-7.68-2 


66-6 


85 


83-7 


82-4 


81-1 


79-8 


78-5 


77-2,75-8 


74-4,73 


71-570-C 


68-5670 


65-4 


84 


82-7 


81-4 


80-1 


78*8 


77-5 


76-1174-7 


73-3,71-8 


70-4'68-S 


67-3 65-7 


64-1 


83 


81-7 


80-4 


79-1 


77-8 


76-4 


75-0J73-6 


72-0 


70-7 


69-2^677 


66-164-5 


62-8 


82 


80-7 


79-4 


78-1 


76-7 


75-3 


73-9 


,72-5 


71-0 


69-6 


68-166-5 


64-9'63-2 


61-5 


81 


79-7 


78-3 


77-0 


75-6 


74-2 


72-8 


71-4 


70-0 


68-4 


66-9 65-3'63-762-0 

1 i 


60-3 


~80~ 


78-6 


77-3 


76-0 


74-6 


73-2 


717 


70-3 


68-8 67 2 


657I64-1 62-4i607 


58-9 


79 


77-6 


76-3 


75-0 


73-5 


72-1 


70-7 


69-2 


67-6 66-1 


04-5:62-8.61-159-4 


576 


78 


76-6 


75-3 


73-9 


72-5 


71-0 


69-5 


68-0 


66-5 65-0 


63-3 61-6 59-8 58-1 


56-2 


77 


75-6 


74-2 


72-8 


71-4 


69-9 


68-4 


66-9 


65-3 63-7 


62-l ! 60-3 58-5 56-7 


54-8 


76 


74-6 


73-2 


71-8 


70-3 


68-9 


67-3 


65-8 


64-2 62-5 


60-8'59-l'57-2 55-3 


53-4 


75 


73-6 


72-2 


70-7 


69-2 


67-7 


66-2 


64-6 


63-061-3 


59-5 57-7,55-9:54-0 


52-0 


74 


72-6 


71-1 


69-7 


68-2 


66-6 


65-1 


63-4 


61-860-1 


58-3 : 56-4'54-5i52-5 


50-4 


73 


71-5 


70-1 


68-6 


67-1 


65-5 


64-0 


62-3 


60-6 58-8 


57-0 55-1 531151-1 


49-0 


72 


70-5 


69-1 


67-5 


66-0 


64-4 


62-8 


61-1 


59-3 57-5 


55-753-7 51-7|49-6 


47-3 


71 


69-5 


68-0 


66-5 


64-9 


63-3 


61-6 


59-9 


58-l ! 56-2 


54-4 52-4 50-3J48-1 


45-7 


70 


^ 


67-0 


65l 


63-8 


62-2 


6¥5 


587 


5tPJ BlFd 


53~0'51-0 48 7 8i46-5 


44-1 


69 


67-4 


66-0 


64-3 


62-7 


61-0 


59-3 


57-5 


55-6 53-7 


51-6|49-5 47-3144-9 


42-4 


68 


66-4 


64-9 


63-2 


61-6 


59-9 


58-1 


56-3 


54-352-3 


50-2 48-0 45-7I43-2 


40-5 


67 


65-4 


63-8 


62-2 


50-5 


58-7 


56-9 


550 


53-051-0 


48-8;46-5 44-1141-5 


38-8 


66 


64-4 


62-7 


61-1 


59-3 


57-5 


55-7 


53-7 


51-7,49-6 


47-3.45-0 42-4:397 


36-8 


65 


63-3 


61-7 


60-C 


33-2 


56-4 


54-5 


52-5 


50-4,48-2 


45-8 43-4 40-71379 


34-8 


64 


62-3 


60-6 


58-9 


57-1 


55-2 


53-2 


51-2 


49-0 46-7 


44-3!41-7 39-0136-0 


32-7 


63 


61-3 


59-6 


57-8 


55-8 


54-0 


520 


49-8 


47-645-1 


42-7J40-1 37-1134-0 


30-5 


62 


60-3 


58-5 


56-7 


54-8 


52-8 


50-7 


48-5 


46-2437 


41-l | 38-3 | 35-2i31-9 


28-2 


61 


59-2 


57-4 


55-5 


53-6 


51-5 


49-4 


47-1 


41-7 42-2 


39-4 36-4 33-2|29-7 


25-7 


60 


58-2 


56-3 


54-4 


52-4 


50 : 3 


48-1 


457 


43 T 2 40 T 6 


37 : 7 , 34 : 6 ( 31 T i!273 


23-0 


59 


57-2 


55-3 


53-3 


51-2 


49-1 


46-8 


44-3 


41-739-0 


35-9 32-6 28-9,24-8 


20-1 


58 


56-1 


54-2 


52-2 


50-0 


47-8 


45-4 


42-9 


40-137-2 


34-0 30-5 26-6I22-1 


17-0 


57 


55-1 


53-1 


51-0 


48-8 


46-5 


44-0 


41-4 


38-5 35-5 


32-l28-3:24-l:19-2 


13-5 


56 


54-0 


52-0 


49-8 


47-6 


45-2 


42-6 


39-8 


36-8 33-6 


30-0 26-021-4J16-1 


9-5 


55 


53-0 


50-8 


48-6 


46-3 


43-8 


41-1 


38-2 


35-131-8 


27-8 23-4 


18-4 12-4 


4-9 


54 


51-9 


19-7 


1-7-5 


45-0 


42-4 


39-6 


36-6 


33-3 29-7 


25-6 20-8 


15-3 


8-5 


-0-2 


53 


50-9 


48-6 


16-2 


43-8 


41-1 


38-1 


34-8 


31-327-4 


230 178 


11-5 


3-7 




52 


49-8 


17-5 


15-1 


12-4 


39-6 


36-6 


33-2 


29-7 25-3 


20-514-8 


78 


-1-4 




51 


48-8 


46-4 


43-8 


411 


38-2 


35-0 


31-4 


27-422-9 


177!ll-3 


3-3 






50 


47-7 


45-2 


426 


39-7 


36-6 


2^3 


29-5 


WsWa 


147 


74 


-2-0 






49 


46-6 


44-1 


41-3 


38-4 


35-1 


31-6 


27-5 


23-0:177 


11-2 


2-9 








48 


45-5 


42-9 


10-0 


37-0 


33-5 


29-7 


255 


20-614-7 


73 


-2-4 








47 


44-4 


41-7 


38-7 


35-5 


31-9 


27-9 


23-3 


17-9 


11-4 


3-1 










46 


43-4 


40-5 


37-4 


340 


30-1 


25-7 


20-8 


14-8 


7-4 


-2-6 










45 


12-2 


39-3 


36-1 


32-5 


28-4 


23-9 


18-5 


12-0 


3-6 












44 


11-1 


38-1 


34-7 


30-9 


26-2 


21-7 


15-8 


8-5 


-1-2 












43 


40-1 


36-8 


332 


29-3 


24-7 


19-4 


12-9 


4-6 


-7-0 












42 


38-9 


35-6 


31-8 


27-6 


22-7 


16-9 


9-7 


0-2 














41 


37-8 


34-3 


30 3 


25-8 


20-b 


14-3 


6-2 


-5-0 














40 


36-7 


33-0 


28-8 


23-9 


18-1 


11-4 


2-2 

















APPENDIX. 



347 



TABLE XII. — Continued. 
Observations on the Wet and Dry Bulb Thermometer. 



15 

ioH 

68-8 
67-5 
66-3 
65-0 
63-7 
62-4 
61-1 
59-8 
58-5 



16 

681 
67-2 
65-9 
64-7 
63-3 



57-1 

55-7 

54-2 

52-8 

51-3 

49 

48-2 

46 

45-0 

43-3 

41-5 

39-7 

37 

35-S 

33-7 

31-5 

29-2 

27 

24-0 

21-2 

181 
14-6 
10-8 
. 6-4 



17 

66^8 
65-6 
64-3 
63-0 
61-6 



62-0 60-3 



60-7 
59-4 
58-0 
56-6 

5fr2 

53-7 
52-2 
50-7 
49-2 
47-6 
46-0 
44-2 
42-5 
40-6 

38l 

36 
34-7 
32-5 
30-2 
27-8 
25-2 
22-3 
19 
15-9 
12-2 
7 



59-0 
57-5 
56-1 
54-7 

5&2 

51-7 
50-1 
48 5 
46-9 
45-2 
43-5 
41-6 
39-8 
37-8 
35^8 
33-6 
31-4 
29-0 
26-4 
23-6 
20-6 
17-3 
13-7 
9-6 



65-2 
63-9 
62-6 
61-3 
59-9 
58-5 
57-1 
55-6 
54-2 
52-7 



18 



51- 

19 

18 

46' 

44 

42 

40 

39' 

36 

34 

32-5 

30-2 

27-7 

25-0 

22-1 

18-8 

15-3 

11-4 



63-6 
62-2 
60-9 
59-5 
58-1 
56-6 
55 2 
53-7 
52-1 
50-6 
49l) 
47-3 
45-6 
43-8 
420 
40-1 
38-1 



19 



46 

15 
43 

11 
39 
37 
35 
36-0132 



20 | 21 

6T9'60l 
60-5 ! 58-7 
59-1I57-2 
57-7155-8 
56-2154-2 
54-7J52-7 
53-2 51-1 



51-6 
500 

48-4 



49-5 
47-8 
46-1 



33-8 
31-4 
29-0 
26-3 
23-5 
20-4 
17-0 
13-2 



44-3 

42-4 

40-4 

38-4 

36-3 

34-1 

31-7 

8J29-2 

4 26-5 

8 23-7 



25-0 
220 
18-8 
15-1 



20-5 
17-1 



22 23 I 24 



58-3 
56-9 
55-3 
53-8 
52-2 
50-6 
48-9 
47-2 
45-4 
43-6 



41-7 

39 

37-6 

35-4 

33-1 

30-7 

28-1 

25-3 

22-3 



454-4 
9 52-9 
3'51-2 

•749-6 



524 
50-8 
49-0 
47-3 
45-5 
43- 
41-6 
39-6 
0!40-3 37-4 
38-2 35-2 



l'47-8 
4,'46-l 
644-2 

8 ! 42.3 



25 



390 36-0 
36-8 33-7 



34-6 
32-2 
29-7 
27-0 



31-2 



26 



50 3 

48 

46-7 

44-9 

43-0 

41-0 

38-9 



27 

481) 
2 
44-3 
42-4 



28 
4513 



5 46 



30 



348 



APPENDIX. 



S3 

a 

o 

O 

i-4 — 

— H C 

^ .5 

O 

3 

H 









i 


£ 

o 
o 


Air 
etres 
aken 


ping hourly 

nrly. 

ated respira- 
, 17° C. 
through yen- 


-3 

bo 






£ 




CO 

o 
o 


>> 

c 


t 6 ■ 


3 

CO 


1 




■a 

Q 

71 

"3 


O 

.3 
-- 

o 

a 
jo 






£ 


3° S 3 

,3 ® § 

"3 J<! § 


s' %2. % &o 


- 

3 
— 


03 

£ 





IS 

o 


CO 

o 

Cfl 


o 

W 03 

.£ £ 

> -3 

e e 


o " l- 

S t £ 
£ < o 


p ft a Su 

£ S^^^ 

d gv-Sj 3 

as .- u O — . 


a 
p 

3 


3 

i* 




3 

CO 


"oo 

cS 


o to 


fjiij 


g 1 3 1 3 •■« 


O 

'-G 

3 




1"3 




O 


00 


s 

3 


© "5 




3: 


tog 




3 
m 

w 

S3 


3 
bo 

c 


- 


> 3 

3 I 

Bui 


- — ~- r ' 2 


^2 .|gg,S 


— 
CO 


.£ = 

3 ^ 




3 
£ 

- 
c 
o 


o - 2 r 

C V 55 C 

£ -ill 3? 


1 L "- "S - 'S - - ^ - = " - —" 


1 115 

5 . 3-= fi 
= t ° = 3 

3 3 3'ii 

-—--: = 




"3 

a 
'3. 


III J §'n||1|i 


: - ~ — ■ rt* - 3 * J 


X w ^ .- 00 

5 > 3 £ a 




a 


Jj 


i 


^ S ^ 


<j § § 


■a c 0=3 


S-l 


.= §£ 




H 


< 


c 


"a t, —J 




C£ 2< £ 


< 


<S< 




^---»~- 


• g g O 3 


=' 






Sep cp 


p ■? <?* 


t^ 




i> 


>"5 " ' (3, — 


| 






o o -^ 


^ —> <n 


6 




Tf«b 


'»|^5 „-s s 


= 






^l-: o 


° r 1 ? 


r 




b- CM 










"*^ k 


i — b 


cb 




b- CM 


>"=-=. 5"s 


3 












«o 


• "o bD = s ■ 


J 




c 


o a 


to 


8 


s 


OO 


= = - = = tc i 


. CM 
















Q-2-2 gag 




CM 




-x s 


cs co os 


n * * ^1 <n 


CM 


!??b»C0 


"~ 












* +- 




... — 


3 t, o C 






~ 


o o 


■<* JO t-H 

us «o OJ 


2 g g § g 


1 


— OSb« 




23 "a 








C5 




_ rt i-i — CD 























.A 


i *?• 


l> 


r 


oo o 


p- r ° 


p p O O C> 


O 


poo 


So s 


-• b- 


s 


i 


SS g 


00 •— b. 

o — — 


m ?3 55 oJ 


1 


oosb 
w X 




"5 0* 


CM 




o c» 


CJ CO T- 


cm t^ t^ t- 


O 


O ?? OS 


O 










— CN 







L- CM 


Ills 


-■= 




L _ 


sprft GO 


cp p cp 


N ^ N S IO 


tp 


1ft 
W O CM 


5-2.5 & 


£> 


6 


so 


a b o 


ji i >3 


M O •* i) (j* 


CM 


Tf«CM 


SI- 
S'! 3 


•_ _ 


CD 


S3 


52^ ^h 


CM CM O 


—1 rf 




OCM 


II 


OS 
3 


Si 


— 55 55 


^5 S § 


^5 S 




6* OS 
CM CM 


5-- 


CM 


!N C^ CN 


CM CN N 


(M OJ 




CM CM 




co 


2~~ 


^ 












a 


£ a. 


u 60 

S .£ 






3 








!2i ^ 






TJ 




- 
- 


J. 


DO 

o 


"3 


i 1 






| 


o 


o 


m 


C3 

^ 3 


O^ "3 - 3 

3<£ -a £ i» 






° 


s 


a 


'= s 


£ ih^O 


02 O 


•S - 2 > 




GO 

Cfl 




'3 
"i 

c 


-a 

5 
O 

JL 


■5 

a 

'.£ ~ 

r :/ 

-.3 

.a g 


5 = 

O g 


3 C S cd 

— Geo 


r 1 SI III 

14 13 1 1 | 

= sod ^J = a Q 
o"=-5b <;/} ©"0-° 

l!l!?lilHl, 


HI 

CO* 

3_ 

s 

6 


X 
O 

3 . C3 
3"r ~ 

111 
O »► 

d aT «T 


■ 


£ 2, 


E § 


5" J 


?ll" 


w -^ £T ^ 

j3 ci w> 5 


3 .3 — O O O = 


3. 


111 


_a 


cc 


02 


< 


H £ O 


c 


Occ 02 




" 


s 


E 


^^^ 




^^ S S b 
" x x, 







APPENDIX. 349 



TABLE XIV. 

Constitution of the Atmosphere. 

Dumas and Boussingault analyzed atmospheric air by fixing its oxygen 
on copper, which was weighed; the azote was also collected and 
weighed. 

1000 parts of air at Paris contained by weight : — 

Oxygen. Azote. 

April 27, fair weather, 229.2 770-8 

« a « « 229.2 770.8 

« 28, " " 230.3 769.7 

" « « « 230.9 769.1 

« 29, " " 230.3 769.7 

« « " " 230.4 769.6 

May 29, rainy, 230.1 769.9 

July 20, mid-day, rainy, 230.5 769.5 

" 21, midnight, clear, 230.0 770.0 

« 26, mid-day, clear, 230.7 769.3 

Mean, .230.2 769.8 

By volume, 208 792=1000 



Consumption of Oxygen and Formation of Carbonic Acid. 

From experiments of Dumas on himself, it appears that about twenty 
cubic inches were received into the lungs at each inspiration, and from 
fifteen to seventeen inspirations per minute. The expired air contained 
from three to four per cent, of carbonic acid, and had lost from four to 
six per cent, of oxygen. These data, for each day of twenty-four hours, 
give, 

16 insp. X 20 cubic inches = 320 cubic inches expired per minute. 
19,200 " " " hour. 

460,800 « « " day 



350 



APPENDIX. 



TABLE XV. 

A Table of Mean Temperatures of the hottest and coldest months. 





Latitude. 


Longitude. 


Mean Temp, of 


Authorities. 


Warm- 


Coldest 








est 
.Month. 


Month. 




St. Petersburgh, 


59 56 N. 


30 19 E. 


65-660 


8-60O 


Humboldt. 


Moscow, 


55 45 N. 


37 32 E. 


70-52 


608 


" 


Melville Island, \ 


74 47 N. 


110 48 W 


39 08 

42-41 


-35-52 
-3219 


Hugh Murray. 
Ed. Phil. Journal. 


Copenhagen, 


55 41 N. 


12 35 E. 


65 66 


27-14 


Humboldt. 


Edinburgh, 


55 57 N. 


3 10W. 


59-36 


38-30 




Geneva, 


46 12 N. 


6 8E. 


66-56 


3416 




Vienna, 


48 12 N. 


16 22 E. 


70-52 


26 60 




Paris, 


48 50 N. 


2 20 E. 


65-30 


3614 




London, 


51 30 N. 


5W. 


64-40 


37-76 




Philadelphia, 


39 56 N. 


75 16 W. 


77-00 


32-72 




New York, 


40 40 N. 


73 58 W. 


80-70 


25-34 




Pekin, 


39 54 N. 


116 27 E. 


84-38 


24-62 




Milan, 


45 28 N. 


9 11 E. 


74 66 


3614 




Bordeaux, 


44 50 N. 


34 W. 


73-04 


41-00 




Marseilles, 


43 17 N. 


5 22 E. 


74-66 


44-42 




Rome, 


41 53 N. 


12 27 E. 


77-00 


42-26 




Funchal, 


32 37 N. 


16 56 W. 


75-56 


64-04 




Algiers, 


36 48 N. 


3 1 E. 


82-76 


60-<H 




Cairo, 


30 2N. 


30 18 E. 


85-82 


56-12 




Vera Cruz, 


19 11 N. 


96 1 W. 


81-86 


71-06 




Havanna, 


23 10 N. 


82 13 W. 


83-84 


69-98 




Cumana, 


10 27 N. 


65 15 W. 


84-38 


7916 




Canton, 


23 ION. 


113 13 E. 


84-50 


57-00 


Anglo-Chinese Calendar. 


Macao, 


22 10 N. 


113 32 E. 


86-00 


63-50? 


" " " 


Canaries, 


28 30 N. 


16 00 W. 


78-90 


63-70 


Brande's Journal. 


Lohooghat (5800 } 
feet above the > 
sea,) ) 

Fattehpur, 


29 23 N. 


79 56 E. 


69-34 


43-57 


S Trans. Med. Phys. Soc. 
\ Calc. 


25 56 N. 


80 45 E. 


74 94 


58-74 


Gleanings in Science. 


Gurrah Warrah, 


23 10 N. 


79 54 E. 


87-45 


60-23 


<( «« (i 


Calcutta, \ 


22 40 N. 


88 25 E. 


85-70 


66.20 


IS It 11 




_ 


86-86 


70-10 


Journal As. Soc. 


Ava, 


21 51 N. 


95 98 E. 


88-15 


6412 


Gleanings in Science. 


Bareilly, 


28 23 N. 


79 23 E. 


91-91 


56 50 


" " " 


Chunar, 


25 9N. 


82 54 E. 


90-00 


58-00 


Ed. Ph. Journ. 


Cape of Good ~) 
Hope (Feld- [ 
hausen,) J 

Bahamas, 












34 23 S. 


18 25 E. 


74-27 


57-43 


Herschel (MSS.) 


26 30 N. 


78 30 W. 


83-52 


69 07 


Hon. J. C. Lees (MSS.) 


Swan River, 


32 00 S. 


115 50 E. 


78-00 


54-84 


Milligan. 


Bermuda, 


32 15 N. 


64 30 W. 


76-75 


57-90 


Col. Emmett. 



APPENDIX. 



351 



TABLE XVI. 

The following proportions between the Mean Temperature of the earth, 
as indicated by springs, and that of the atmosphere, have been collected 
from various sources. 



Names of Places. 



Berlin, ...... 

Carlstrom, .... 

Upsal, 

Paris, 

Charleston, . . . 
Philadelphia, . . . 

Virginia, 

Massachusetts, . . 

Vermont, 

Kaith, (Scotland,) . 
Gosport, (England,) 
Kendal, (do.) . 
Keswick, (do.) . 
Leith, (Scotland,) . 
South of England, . 
Torrid Zone, . . . 



Authority. 



Wahlenberg, 



(Catacombs,) 
Volney, 
u 



Dewey, 
Volney, 
Ferguson 
Watson, 



Rees' Cyclo, 
Volney, . . 



Temp. 

of 
Earth. 



49-28° 

47-30 

43-70 

53-00 

63-00 

5300 

5700 

47-21 

4400 

47-70 

52-46 

47-20 

46-60 

47-30 

48-00 

63-00 



Mean 
Temp, of 
Atmos- 
phere. 



46-40° 

42-03 

42-08 

51-00 

68-00 

53-42 

57-00 

44-73 

56-00 

47-00 

51-42 

47-04 

48-00 

48-36 

50-62 

81-50 



30* 



352 



APPENDIX. 



TABLE XVII. 

Showing the Specific Gravity of different kinds of timber. 



Box, . . . 

Plum-tree, 
Hawthorn, 
Beech, . . 
Ash, . . . 



Yew, .... 

Elm, 

Birch, .... 
Apple, .... 
Pear, .... 
Yoke-elm, . . 
Orange-tree, . 
Walnut-tree, . 
Pine, .... 
Maple, .... 
Linden-tree, 
Cypress, . . . 
Cedar, .... 
Horse chestnut, 
Alder, .... 
"White poplar, . 
Common poplar, 
Cork, .... 



I. 


II. 


— 


942 


— 


872 


— 


871 


852 





845 


670 


807 


744 


800 


568 





738 


733 


734 





732 





728 


705 








660 


657 


763 





645 


604 


559 


598 





561 








551 





538 


529 





383 


387 


240 






# # * The column I., in the above table, exhibits the specific gravity 
of different woods, adopted by the Annuaire du Bureau des Longitudes. 
The second column contains the results obtained by M. Karmarsch. 



APPENDIX. 



353 



TABLE XVIII. 



Solutions for the impregnation of wood which is exposed to the atmos- 
phere, for the purpose of preserving it from decay. 



Tar. 

Sulphate of Copper. 

Sulphate of Zinc. 

Sulphate of Iron. 

Sulphate of Lime. 

Sulphate of Magnesia. 

Sulphate of Barytes. 

Sulphate of Soda. 

Alum. 

Carbonate of Soda. 

Carbonate of Potash. 

Carbonate of Barytes. 

Sulphuric Acid. 

Acid of Tar, (pyroligneous acid.) 

Common Salt. 

Vegetable Oils. 

Animal Oils. 

Coal Oil, (Naphtha,) 

Resins. 

Quick-lime. 



Glue. 

Corrosive sublimate.* 

Nitrate of Potash. 

Arsenical Pyrites water, — (water 
containing arsenical acid.) 

Peat Moss, (containing tannin.) 

Creosote and Eupion. 

Crude Acetate, or pyrolignite of iron. 

Peroxide of Tin. 

Oxide of Copper. 

Nitrate of Copper. 

Acetate of Copper. 

Solution of Bitumen, in oil of tur- 
pentine. 

Yellow Cromate of Potash. 

Refuse Lime-water of Gas-works. 

Caoutchouc, dissolved in naptha. 

Drying Oil. 

Beeswax, dissolved in turpentine. 

I Chloride of Zinc. 



* Corrosive sublimate is one of the most efficient of all these antiseptic applications. 
It was proposed by Mr. Kyan as a preventive of dry rot, under the idea of its acting 
as a poison to the fungi and insects, which were the supposed cause of the disease. 
But this explanation of the action of corrosive sublimate is no longer tenable, as it ia 
generally admitted that the fungi and insects are not to be considered the origin, but 
the result, of the dry rot. It has been suggested that its action depends on the forma- 
tion of a compound of lignum, or pure woody fibre, with corrosive sublimate, which re- 
sists decomposition in circumstances where pure lignum is liable to decay. But pure 
lignum possesses no tendency to combine with corrosive sublimate. The action of 
this substance is in reality confined to the albumen, with which it unites to form an 
insoluble compound, not susceptible of spontaneous decomposition, and, therefore, in- 
capable of exciting fermentation. Vegetable and animal matters, the most prone to 
decomposition, are completely deprived of their property of putrefaction and fermenta- 
tion by the contact of corrosive sublimate. It is on this account advantageously em- 
ployed as a means of preserving animal and vegetable substances. Its expensiveness 
in this country is a great obstacle to its extensive employment on timber used for build- 
ing purposes, for fences, bridges, &c. There is scarcely any antisceptic application 
so effectual. By Mr. Kyan's process, the timber to be impregnated, is sawed up into 
planks, and soaked for seven or eight days in a solution containing one pound of cor- 
rosive sublimate to five gallons of water. The impregnation may be easily effected in 
an open tank ; though the best way is to impregnate the timber by placing it in an 
air-tight box, from which the air has been exhausted as much as possible by a pump. 
The solution then enters the pores of wood freely, being pressed into them by a force 
equal to about one hundred pounds to the square inch. — Parnell's Applied Chemistry. 



354 APPENDIX. 



TABLE XIX. 

Table showing the Heating Power of different kinds of "Wood, drawn 
by MM. Peterson and Schodler, from the quantity of Oxygen required 
to burn them. 

Names of Trees. Oxygen required to burn them. 

Tila Europea, lime, 140-523 

Ulmus suberosa, elm, 139-408 

Pinus abies, fir, 138-377 

Pinus larix, larch, 138-082 

JEsculus hippocastanum, horse-chestnut, 138-002 

Buxus sempervirens, box, 137-315 

Acer campestres, maple, 136-960 

Pinus sylvestris, Scotch fir, 136-931 

Pinus pinea, pitch pine, 136-886 

Populus nigra, black poplar, 136-628 

Pyrus communis, pear tree, . 135-881 

Juglans regia, walnut, 135-690 

Betula alnus, alder, 133956 

Salix fragilis, willow, 133-951 

Quercus robur, oak, 133-472 

Pyrus malus, apple-tree, 133-340 

Fraxinus excelsior, ash, 133-251 

Betula alba, birch, 133.229 

Prunus cerasus, cherry-tree, 133-139 

Robinea pseudacacia, acacia, 132-543 

Fagus sylvatica, white beach, 132-312 

Prunus domestica, plum, 132-088 

Fagus sylvatica, red beach, 130-834 

Diospyros ebenum, ebony, 128-178 



APPENDIX. 



355 



TABLE XX. 



Difference in Weight of two columns of Water, each one foot high, at 
various Temperatures. 



Difference in 






temperature 

of the two 

columns of 

water in 

degrees of 

Fahrenheit's 

Scale. 


Difference in weight of two columns of water, 
contained in different sized pipes. 


Difference of a 

column one foot 

high. 




1 inch dia. 2 inches dia. 


3 inches dia. 


4 inches dia. 


per square inch. 


2° 


grs. weight. 

1-5 


grs. weight. 
6-3 


grs. weight. 
14-3 


grs. weight. 
25-4 


grs. weisht. 
2-028 


4 


31 


12-7 


28-8 


51-1 


4-068 


6 


4-7 


19-1 


43-3 


767 


6-108 


8 


6-4 


25-6 


57-9 


102-5 


8-160 


10 


8-0 


32-0 


72-3 


128-1 


10-200 


12 


9-6 


38-5 


87-0 


154-1 


12-264 


14 


11-2 


45-0 


101-7 


180-0 


14-328 


16 


12-8 


51-4 


116-3 


205-9 


16-392 


18 


14-4 


57-9 


131-0 


231-9 


18-456 


20 


16-1 


64-5 


145-7 


258-0 


20-532 



* # * It will be observed in the above table that the amount of motive 
power increases with the size of the pipe ; for instance, the power is 
4 times as great in a pipe of 4 inches diameter as in one of 2 inches. 
The power, however, bears exactly the same relative proportion to the 
resistance, or weight of water to be put in motion in all the sizes alike ; 
for, although the motive power is 4 times as great in pipes of 4 inches 
diameter, as in pipes of 2 inches, the former contains 4 times as much 
water as the other. The power and the resistance, therefore, are rela- 
tively the same. 



INDEX TO THE ILLUSTRATIONS, 



PART I. 



SECTION I. 

Fig. Page. 

1 Elevations of hot-house roofs, 35 

2 Difference of elevation of the sun's rays at Philadelphia and London, . . 36 

3 End section of a forcing pit, . . . 39 

4 Ground plan and elevation of forcing pit, 41 

5 End section of a stove, 42 

6 Polyprosopic forcing house, 43 

7 Cambridge pit, 43 

8 Saunders' pit, 48 

9 Curvilinear cold pit, 46 

10 Dung bed with frame for forcing, 46 

11 Portable glass frame, 48 

12 Portable plant protector, 48 

13 Ground plan of an extensive framing ground, 51 

14 Range of graperies at Clifton Park, 53 

15 Single-roofed grapery, 55 

16 Span-roofed house on the same scale, 55 

17 Single-roofed curvilinear grapery, 57 

18 Double-roofed house of the same plan, 57 

19 Polyprosopic grapery, 61 

20 Ground plan of do., 61 

21 Ridge and furrow roof, 65 

22 Range of small houses, 69 

23 Ornamental grapery, 71 

24 End section of green-house, 76 

25 Perspective view of span-roofed green-house, 77 

26 Range of plant-houses, 78 

27 Ornamental plant-house, 80 



SECTION II. 

28 Roof trellises, ■ . 85 

29 Interior trellises, 86 

30 Upright trellises, 87 

31 Roof trellises and open border planting, 87 

32 Interior ground plan of a conservatory, 95 



ILLUSTRATIONS. 



357 



PART II. 

Fig. P-^b- 

33 Williams' furnace for prevention of smoke 3 .149 

34 Jeffreys' smoke-precipitating furnace, 151 

35 Improved arch boiler, • 179 

36 Common boiler, 179 

36 A Circular boiler and pipes, 185 

37 Ground plan of poimaise heated green-house, 197 

38 End section of do., -193 

39 Longitudinal section of do., • • 199 

40 Combination of hot water and hot air, • 201 

41 Four houses heated with one boiler, 204 

42 Boiler and supply box, • 205 

B Supply cistern, 205 

43 Tank method of heating, 210 

44 Tank of galvanized zinc, 214 

45 Wooden tank for retention of heat, 216 

46 End section of do., 216 

47 Plant pits heated by wooden tanks, -227 

48 Arched borders heated with hot-water pipes, 230 

49 Chambered border heated with tanks, 233 

50 Covered hot wall, 241 



PART III. 

52 Method of ventilating lean-to houses by pulleys, 277 

53 End section, showing the apertures for ventilation through the walls, . 277 

54 End section of span roof, showing ventilation at top, 278 

55 Showing the ventilator enlarged, 279 

56 Front ventilation by rachet wheel, 280 

57 Movement of the atmosphere from the floor of the house, ....... 289 

58 Common methods of ventilation, 291 



TABLES. 



I. Table of the expansive force of steam in pounds per square inch, for tem- 
peratures above 212° Fahrenheit, 335 

II. Table of the quantity of vapor contained in atmospheric air at different 
temperatures, when saturated, 336 

III. Table of the expansion of air and other gases by heat, when perfectly 
free from vapor, 337 

IV. Table of specific gravity and expansion of water at different temper- 
atures, 338 

V. Table of specific heat, specific gravity, and expansion by heat of different 
bodies, 339 

VI. Table of the effects of heat, 340 

VII. Table of the quantity of water contained in 100 feet of pipe of different 
diameters, 341 

VIII. Table showing the effects of wind in cooling glass, 341 

IX. Experiments on the cooling effect of windows, 342 

X. Weights of watery vapor in one cubic foot of air, at dew points from 0° to 
100° Fahrenheit, 344 

XL Dalton's table of the force of vapor, from 32° to 80°, 345 

XII. Table for ascertaining dew point by observations on the wet and dry 
bulb thermometer, 346 

XIII. Table of the analysis of confined air, 348 

XIV. Constitution of the atmosphere ; consumption of oxygen, and formation 
of carbonic acid, 349 

XV. Table of mean temperatures of the hottest and coldest months, . . 350 

XVI. Mean temperature of the earth and of the atmosphere, 351 

XVII. Specific gravity of different kinds of timber, 352 

XVIII. Solutions for the impregnation of wood which is exposed to the at- 
mosphere, for the purpose of preserving it from decay, 353 

XIX. Heating power of different kinds of wood, drawn from the quantity 
of oxygen required to burn them, 354 

XX. Difference of weight of two columns of water, each one foot high, at 
various temperatures, 455 



INDEX. 

PART I. -CONSTRUCTION. 

SECTION I. 

SITUATION. 

Site and position. — What is to be understood by site and position. — Cir- 
cumstances to affect the position of a hot-house.— Avoid hare, elevated spots. — ■ 
Reasons for so doing. — For shelter. — For beauty and effect, 13 

Terraces. — Their origin, and use round horticultural buildings. — The un- 
sightliness of turf terraces. — Architectural terraces. — Description of a terrace 
at a gentleman's residence. — Effect of trees. — Effect without trees. — Choice 
of position decided by other circumstances, 15 

Aspect. — Best aspect for lean-to houses. — Reasons for choosing a south- 
eastern aspect. — Aspect for span-roofed houses. — The aspect of conserva- 
tories. — Unsuitable conservatories, 20 

SECTION II. 

DESIGN. 

General principles. — Object of hot-houses. — Agents of vegetative growth. — 
Reasons why bad structures are so generally erected in this country. — Mansion 
architects. — Their incapacity for erecting horticultural buildings. — Fitness for 
the end in view. — Solid, opaque conservatories. — Conservatory at Brookline. 
— Absurdity of spending large sums on conservatories. — Observations of an 
architect. — Massive conservatories, 25 

Light a primary object. — Wonderful effects of light on vegetables. — Theory 
of the transmission of light. — Rays of light reflected from transparent sur- 
faces. — Action of light upon plants. — Effects of different rays. — Light which 
has permeated yellow media. — Light which has permeated red media. — Light 
which has permeated blue media. — Difficulty of obtaining pure colors. — 
Amount of assimilation and perspiration in plants. — Necessity of making plant- 
houses transparent on all sides, .29 

Slope of hot-house roofs. — Much depends on the angle of elevation. — Prin- 
ciples to guide the inclination of hot-house roofs. — Elevations of roofs in 
England. — Figure representing different elevations. — Figure showing the dif- 
ference of latitude between London and Philadelphia. — Application of these 

31 



360 INDEX. 



principles. — Error committed in laying hot-house roofs too flat. — Table show- 
ing the number of rays reflected at different angles. — Circumstances on which 
the slope of roofs depends, 34 



SECTION III. 
STRUCTURES ADAPTED TO PARTICULAR PURPOSES. 

Forcing-houses, culinary -houses, &c. — Purposes of their erection. — Section 
of a forcing-pit figured and described. — Large forcing-pit figured and described. 
— Dimensions of winter forcing-houses. — Skill required in the forcing of fruit 
in winter. — Polyprosopic forcing-houses figured and described. — Advantages 
of polyprosopic roofs, 30 

Pits. —The Cambridge pit. — Saunders' forcing-pit figured and described. — 
Curvilinear roofed cold pits. — Dung beds. — Temporary frames. — Plant pro- 
tectors. — Figures and descriptions of them, 43 

Framing ground. — Its purposes. — General condition of this department. — 
Appropriate site for it. — Ground plan and disposition of framing ground, . 49 

Orangeries, graperies, &c. — Latitude given in their construction. — Repre- 
sentation of a range of cold-houses at Clifton Park. — Size of eold-houses. — 
Figures of lean-to and span-roofed houses. — Figures of doable and single- 
roofed curvilinear houses, 54 

Objections raised against curvilinear houses in England. — Properties pos- 
sessed by curvilinear houses. — Reflection and refraction of light by them. — 
Their adaptability for grape-growing. — Gable ends. — Objections to them, . 58 

Polyprosopic houses. — Figures and descriptions of do. — Double-roofed 
houses of this kind. — Cold vineries. — Disadvantages attending them. — 
Front wall of hot-houses. — The height of do. — Objections to upright fronts. — 
Parapet walls, 60 

Ridge and furrow-roofed houses. — Figure and description of a house of this 
kind. — Directions for building ridges and furrows. — Glazing of d&. — Advan- 
tages of do. — Principle of their construction, . 64 

Cold vineries. — Range of small houses figured and described. — Advantages 
of small houses over large ones, . . 67 

Green-houses, conservatories, &e. — Distinction between green-houses and 
conservatories. — Amalgamation of the two together. — Appropriation of green- 
houses in summer. — Span-roofed green-houses preferable to single-roofed ones. 
— Beauty of well-grown plants. — Impossibility of growing plants well in opaque 
houses. — Proportions of a green-house, 73 

Plan of green-house, and description. — Prospective view of green-house. — 
Range of green-houses. — Height of plant-houses. —Errors in making them too 
high. — Conservatory at Regent's Park Botanic Garden. — Principles of design 
and taste displayed. — Advantages of low-roofed plant-houses, . . . . . .76 



SECTION IV. 

INTERIOR ARRANGEMENTS. 

Arrangements for forcing-houses, culinary-houses, &c. — Trellises and meth- 
ods of fixing trellises. — Roof trellises. — Centre trellises. — Cross trellises. 
— Trellises for double houses, 84 

Interior of green-houses. — Slope of green-house stages. — Green-houses for 
promiscuous plants. — Width and height of green-house shelves. — Stages for 
small plants, &c., 87 

Conservatories, Orangeries, &e. — Houses for growing large plants. — Con- 
servatory beds. — Level of do. — Objections to the general form of conserva- 
tory beds. — Irregular method of laying out the interior of conservatories. — 
This method illustrated in the conservatory at the Royal Botanic Garden, Re- 
gent's Park. — Ground plan of a conservatory laid out in the irregular style. — 
Advantages resulting from this method,. . . . . 89 



INDEX. 361 



SECTION V. 

MATERIALS OF CONSTRUCTION. 

Workmanship. — Bad foundations, &c. — Temporary nature of horticultural 
erections. — Consequence of bad constructed houses. — Superior workmanship. 

— Economy of building substantial houses, ..... 99 

Materials of construction. — Most suitable materials for building hot-houses. 

— Metallic houses — Superior to wood. — Opposition to iron hot-houses. — 
Objections raised. — Objections answered. — Expansibility of copper — Of 
iron. — Power of metals to conduct heat. — Electricity an objection. — Cost 
of iron hot-houses. — Mr. Ressor's iron vinery. — Horticultural structures in 
Europe of iron. — Transportability of materials, &e., .......... 101 



SECTION VI. 

fiLAS'S. 

The physical properties of transparent bodies. — Glass of the palm-house at 
Kew. — Report of Mr. Hunt, from SUliman's Journal of Science. — Calorific 
influence of the glass chosen. — Action of the non-luminous rays of light. — 
Green glass of Mellon i, ................. 106 

Evils consequent on employing bad glass in hot-houses. — Knotted and 
wavy glass. — Its effects. — Resources against bad glass. — Painting and shad- 
ing the glass, — Inconveniencies attending both these methods. — Utility of 
using good glass. — Propriety of manufacturers of glass making good mate- 
rial, 109 

Glazing. — Size of laps. — Glazing roof-sashes. — Objectionable nature of 
broad laps. — The most approved method of making laps. — Curvilinear glaz- 
ing. — Reversed rarvilraear 'glazing. — Puttying the laps. — Glazing ridge and 
furrow roofs. — Anomalous surfaces, 110 

Color of walls. — Considerations in favor of a dark color. — Influence of 
reflected light on dark walls. — Retention of heat by dark-colored walls. — 
Color of the rafters. — Painting of the wood-work of the house with an anti- 
corrosive solution, .......... 113 



SECTION VII. 
FORMATION OF GARDENS. 

Form of the garden and disposition of the ground. — Considerations neces- 
sary for fixing on the site. — Walks. — En trance- walk. — Formation of walks. 
— Different kinds of walks. — The durability and comfort of walks. — Materials 
for the surface of walks. — Form of the surface. — Edges of walks, . . . .116 

Borders and compartments. — Width and size of do. — General rule for lay- 
ing down borders. — Size and number of compartments. — Bad effects of small 
walks, 119 

Walls — their rise. — Forms of walls. — Their height. —Gardens of Mr. 
Cushing, at Water»own. — Hot and flued walls. — Wooden fences. — Com- 
parative economy &t walls and fences, 121 



362 INDEX. 



PART II. -HEATING. 

SECTION I. 

PRINCIPLES OF COMBUSTION. 

The nature and properties of fuel. — Considerations on the subject. — Char- 
acteristics in the use of coals pointed out. — Result of the application of heat 
to coal. — Disengagement of gas. — Gases endowed with the power of giving out 
heat. — Combustibility. —What is combustion. — The heating power of gas, 125 

Inquiry into the combustion of coal gas. — Doctrine of equivalents. — Ob- 
servations of Mr. Parks. — Disproportion between the volumes of the constituent 
parts. — Different kinds of gases generated. —Bulk of gases represented by 
figures, . 132 

Atmospheric air. — Its constituents represented by diagrams. — The com- 
ponent parts of different gases represented by diagrams. — Union of the con- 
stituents. — Chemical law in relation to these gases. — Carbon vapor, . . . 137 

Formation of carburetted hydrogen. — Excess and deficiency of heat-producing 
ingredients. — The union of oxygen with smoke. — Quantity of air required to 
supply the requisite quant it}' of oxygen. — How ordinary furnaces are incapable 
of consuming coal perfectly. —The complete combustion of bodies, . . . -145 

Argand lamp. — Williams' smoke-preventing furnace figured and described. 

— Jeffries' smoke-precipitating furnace figured and described. — Their value 
considered. — Application of these inventions in Europe. — Methods of burning 
smoke, 148 

Construction of furnaces. — For heating large boilers. — For making the 
fuel last a long time. — Considerations necessary to be noticed in building the 
furnace. — The kind of fuel to be consumed. — Size and width of bars. — 
Table for ascertaining the area of furnaces, 153 

SECTION II. 
PRINCIPLES OF HEATING HOT-HOUSES. 

Effects of artificial heat. — Changes produced by it. — Animal and vegetable 
matter decomposed by it. — Hydrogen eliminated by the decomposition of 
water. — Experiments on the effects of heated air. — Heat from brick flues. — 
Iron radiators more injurious than others, 156 

Laws of heat. — Radiation and conduction. — Combined effects of radiation. 

— Proportion they bear to each other. — Table showing the velocities of cooling 
at different temperatures. — Experiments on cooling of iron pipes. — Specific 
heat of air and water. — Horticultural structures different from opaque build- 
ings. — Causes of loss of heat, 158 

Table showing the quantity required to heat given volumes of air. — The 
effects of glass windows ascertained. — Experiments on glass surfaces. — Table 
showing the results. — Specific heat of air and water. — Application to hot- 
house buildings, 164 

SECTION III. 

HEATING BY HOT WATER, HOT-AIR, AND STEAM. 

Practice of heating by hot water. — Its merits considered. — Temperature 
of hot- water pipes. — Weight of steam. — Calculations showing the superiority 
of hot- water pipes. — Permanancy of heat by hot water, 167 



INDEX. 363 



Comparison of hot air with hot water, as a method of heatiug horticultural 
buildings. — Air a bad conductor. — Evaporating pans for supplying moisture. 

— Considered in respect to motion in the atmosphere — in respect to perma- 
nency of heating power. — Water a better conductor. — Experiments on air and 
water as modes of conducting heat, , 171 

SECTION IV. 

HOT-WATER BOILERS AND PIPES. 

Size of boilers, and surfaces necessary to be exposed to the fire. — Adapta- 
tion of the boiler to the apparatus. — Of the boiler and the quantity of water 
contained. — The repulsion of heat by the metal of the boiler. — Table showing 
the proportion the surface exposed to the fire must bear to the quantity of pipe, 176 

Causes tending to modify the proportions to be adopted. — Figures of boilers. 

— Estimated action of the fire upon the boilers. — Material for boilers, . . 179 
Size and arrangement of hot-water pipes most suitable for the purposes of 

heating. — Unequal rate of cooling in the various sized pipes. — The ordinary 
methods of arranging hot-water apparatus. — Advantage of taking the flue 
through the house. — Laying down hot-water pipes. — Expansion of pipes 
when heated. — Supply cisterns, 181 

Impediments to circulation. — Causes of circulation. — Amount of motive- 
power. — Table showing the weight of water at different temperatures. — 
Trifling cause renders an apparatus inefficient. — Methods of increasing the 
motive-power. — The rapidity of circulation in proportion to the motive- 
power, . . _ 184 

Level of pipes. — Errors committed in the level of pipes. — Circulation takes 
place first at the boiler. — Methods of making water circulate in pipes below 
the level of the boiler, 188 

Accumulation of air in pipes. — Provision necessary for the escape of air. — 
Want of attention to this the cause of failures. — The size of air vents. — Diffi- 
culty of finding the proper place to place the air vents, 190 

SECTION V. 
VARIOUS METHODS OF HEATING DESCRIBED. 

Expense attending the ordinary methods of heating. — Polmaise method of 
heating. — Its adoption in houses in this country. — Its origin. — Means em- 
ployed to promote it in England. — Description and figures of this method, . 192 

A method of combining hot air and hot water together. — Figured and de- 
scribed. — Advantages of this method in the generation of heat and saving of 
fuel, 200 

Compound method of heating. — Seven ranges of houses heated by this 
method. — Figure representing four houses heated by this plan. — Figure of 
boiler and box. — Of supply cisterns. — Advantages of this mode of heating. — 
Saving of fuel by it. — Simplicity of working, 203 

Tank methods of heating. — Methods figured and described. — Wooden and 
metallic tanks. — The merits and properties of each. — Utility and simplicitv 
of do., 211 

Fertilization of the atmosphere by tanks. — Dissolving volatile gases in tanks. 
Their use in English nurseries for growing young stock. — Their adaptation to 
amateurs, in small pits, 223 

Representation of plant pits and description. — Uses of these pits. — Protec- 
tion of plants during winter in them, 226 

Chambered vine borders. — Argument in favor of them. — Their utility 
under certain circumstances. — Figure and description of a chambered border. 

— Evidence in favor of them, 228 

Cheap method of forming a chambered vine border. — Comparison of cost of 

it with manure. — Economy of their adoption. — Method of managing them. — 
Coverings of borders, 234 

31* 



364 INDEX. 



Construction of hot walls. — Figure and description of hot wall. — Various 
methods of building hot walls. — Trial of hot walls, covered and uncovered. — 
Foreign grapes may be grown on hot walls. — Grapes produced on hot walls in 
England, 2i0 

New method of propelling heated air by means of machinery — described by 
Mr. Mamock in Gardeners' Journal. — The air propelled by means of a fan, 246 



PART III. -VENTILATION. 

SECTION I. 

PRINCIPLES OF VENTILATION. 

Attention required from gardeners, &c. — Its practical importance. — Power 
of plants to withstand the changes of climate. — Power of vitality possessed 
by seeds. — Power of plants to bear high temperatures. — Of bearing delete- 
rious gases. — Effect of winter-forcing on the odor of flowers — and on the 
flavor of fruits, 248 

Whether vegetation purifies the air. — Opinions of Priestley — of Dr. Dau- 
beny, of Oxford — of Dr. Lindley, of London. — Natural adjustment of the 
atmospherical elements. — Atmosphere of cities. — Benefits of large trees in 
the streets. — New Haven, the effect of trees in it, 252 

Power of plants to absorb carbonic acid. — Gottingen springs. — Property of 
charcoal for absorbing gases. — Table of gases and the quantities absorbed by 
charcoal, 254 

Power of plants to withstand the vicissitudes of temperature. — Theories of 
physiologists. — Dalton's chemical philosophy. — His theory of the relations of 
the atmosphere to heat. — The properties possessed by caloric, 256 

SECTION II. 

EFFECTS OF VENTILATION. 

Effects of admitting cold air into a hot-house. — Moisture carried away. — 
Necessity of keeping "the floors damp. — Plants unlike animals in respect to 
ventilation. — Ventilation not necessary as regards respiration. — Air-tight 
glass cases for plants, 262 

Knight's experiments on grape vines. — The philosophy of this system. — 
Evaporation of moisture on the glass. — Contaminating gases in the atmos- 
phere. — Experiments of Drs. Turner and Christison, ; . .264 

The abstraction of moisture in proportion to the rapidity of the motion of the 
air. — Methods of counteracting this loss. — Thermometric changes not sat- 
isfactory rules for the admission of air, 266 

Quantity of moisture contained in the air. — Its capacity for moisture.^ — 
Estimated quantity of air escaped. — Estimated quantity of moisture escaping 
in the air. — Lofty plant-houses. — Difficulty of managing the atmosphere in 
them, 269 

SE CTION III. 

METHODS CF VENTILATION. 

Improvements of the present methods of ventilation. — Plans adopted to 
modify the influence of draughts. — Motion in the atmosphere. — Machinery 
employed for this purpose. — Detection of currents by a common candle. — 
Propriety of a rapid motion disputed, 273 



INDEX. 365 



Difficulty of managing the atmosphere in large, dome-shaped houses. — 
Covering necessary. — To equalize the temperature. — The natural law of 
equality ineffectual. — The slightest cause disturbs the equilibrium of the air. 
— The extreme sensibility of the air. — Irregularity of its temperature in hot- 
houses. — The causes of this irregularity. — Experiments of Gay Lussac — 
of Rudberg, 275 

A new method of ventilation. — Adapted to lean-to houses. — Figured and de- 
scribed. — Facility with which this method may be wrought, 277 

Method of ventilating span-roofed houses. — Adopted in the new hot-houses 
at Frogmore. — Figures and description of this method, 279 

Methods of airing by the rachet wheels. — By springs. — Superiority of the 
former. — Necessity of having the machinery for ventilation properly erected. — 
Its liability to get out of repair. — Method applauded without merit. — Neces- 
sity of guarding against the applauded inventions of any one, 280 



SECTION IV. 

MANAGEMENT OF THE ATMOSPHERE. 

Atmospheric motion. — Admitting large quantities of cold air. — The results 
of this method. — Questions arising out of these considerations. — The quantity 
of air to be admitted. — Motion affected by various circumstances. — The 
atmosphere of a hot-house influenced by the glazing of the sashes. — Effect 
produced by radiation. — Growth of plants in Wardian cases. — Deterioration 
of air by flues, &c, 284 

Method of airing without opening the sashes. — Figured and described. — 
This method recommended for houses during cold weather in winter, . . . 288 

Common method of ventilating figured and described. — Evils resulting from 
this method. — Action in cold weather, 290 

Contrivance for admitting warmed air into the house over the heating appa- 
ratus. — By a serpentine conductor. — Size of the tubes necessary. — Radiation 
of heat from the surface of the flue. — The effects of the external air neutral- 
ized by this method, 292 

The system of ventilation. — Its object being to prevent a stagnation in the 
atmosphere. — Evils of this method shown and explained. — Mechanical and 
chemical effects of ventilation 293 



SECTION V. 

CHEMICAL COMBINATIONS IN THE ATMOSPHERE 
OF H OT-HOTJSES. 

Nourishment plants ought to receive from the atmosphere. — How to receive 
it. — Starch and sugar. — Their different properties. — Questions arising from 
considerations of their properties. — Experiments on the atmosphere. — The 
importance of oxygen to vegetable life, 296 

Atmosphere from fermenting manure. — Quality of heat generated by it. — 
Impregnation of the atmosphere with ammonia. — Experiments on the atmos- 
phere of a green-house with ammoniacal gas, : . .299 

Composition of ammonia. — Excess of ammonia. — Its suffocating influence. 
— Illustrations of its effects. — Fumigation of plant-houses and pits with 
ammonia. — The cause of luxuriance in plants. — Produced largely from fer- 
menting manure, &c, _ 300 

What guides we have to ascertain the various changes in the atmospheric 
elements." — Disagreeable smell on entering a hot-house. — The cause, and how 
to remedy it. — The important part played by oxygen in this process. — Pro- 
portion of oxygen necessary to vegetables. — Amount contained in atmospheric 
air and water. — Affinity of its elements, 303 



366 INDEX. 

Beautiful adaptation of the atmosphere to plants and animals. — Effect of 
pure oxygen. — Property of watery vapor in vegetable economy. — Subtlety of 
the air. — Necessity of maintaining an adequate supply of aqueous vapor in the 
atmosphere. — Instruments for guiding us in regulating the atmosphere. — In- 
struments much wanted for measuring the respective quantities of the gaseous 
elements, 305 



SECTION VI. 

PROTECTION OF PLANT-HOUSES DURING COLD 
NIGHTS. 

Advantages of protecting bodies. — Conditions of the plants at low temper- 
atures. — Light coverings otherwise useful. — Experiments on the cooling 
effects of wind. — Materials for protecting glazed structures. — Methods of 
protection, 309 

Slight covering that is required to protect plants from frost. — Experiments 
of Dr. Wells on coverings. — Method of covering. — Distance to keep the cov- 
ering from the object protected, • ... 313 

Effects of vertical coverings. — Hoi-izontal coverings. — Coverings of straw, 
etc. — Protection afforded by walls. — Protection of snow. — Warmth afforded 
by the soil to trees in winter, 317 



SECTION VII. 

GENERAL REMARKS ON THE MANAGEMENT OF 
THE ATMOSPHERE OF HOT-HOUSES. 

Adjustment of the artificial to the natural atmosphere. — Observations of 
Knight. — Rest necessary to plants during night. — Cause of the imperfect 
maturation of fruit-tree blossoms. — High night temperatures exhaust the ex- 
citability of the trees. — Plants continue longer in bloom in low night temper- 
atures. — Admission of external air during day. — Difference of climate be- 
tween this country and England, 320 

Rules to be observed by the gardener in charge of hot-houses. — Dutch meth- 
od of forcing. — Excessive moisture — its effects. — Necessity for periods of 
rest to plants. — Changing the period of fructification, 325 



SECTION VIII. 

VENTILATION WITH FANS. 

Construction of ventilating fans. — Methods of using them. — Their adapta- 
tion to horticultural purposes. — Different kinds of fans. — Objects to be ef- 
fected by them. — Requisites to the use of fans. — Windmill ventilators. — 
Their employment in horticultural buildings. — Pump ventilators. — Ventila- 
tion by means of chimney shafts, &c 329 



3477 



*'■ 



